massive cities (3.5)

[Somensjev]

i've been designing a setting, and in it the entire material plane (which isn't infinite) has five continents

now, the capital cities of these continents are incredibly large (very small compared to the continents themselves)

each city is at least 40,075km in circumference, which means a diameter of at least 12,742km, and the buildings/structures can reach heights of up to 8,848m

now, i was wondering if a city this large could actually support itself? (you can buy items of at will teleport for exceedingly low prices, otherwise getting around would be nigh-impossible)

thank you for any and all replies

[Yora]

40,000km happens to be the circumferance of the Earth (which I assume was the reason for your choice), so the scale would be massive with a population in the hundreds of billions.
Which I would assume to be so far off the scale, that it becomes impossible to make any calculated estimates about the required infrastructure.

[Somensjev]

i did choose it because it's the circumference of the earth (just the same as i used the diameter of earth, and the height of mt everest)

population of hundreds of billions? :smallconfused: i didnt think it'd get as high as that (although, it does go up as well, so i guess it's sort of like an earth sized tokyo..?)

[hamishspence]

The city you describe (assuming it's supposed to be a disc rather than the surface of a sphere) would have a surface area of 127.5 million square km. (Pi^radius^radius).

Only 1/4 that of a sphere with that diameter- still a lot.

If you use the population density of a normal city, and up it a bit to account for the much higher skyscrapers, you are going to get a figure of many trillions (a few quadrillion?)

[Somensjev]

The city you describe (assuming it's supposed to be a disc rather than the surface of a sphere) would have a surface area of 127.5 million square km. (Pi^radius^radius).

Only 1/4 that of a sphere with that diameter- still a lot.

If you use the population density of a normal city, and up it a bit to account for the much higher skyscrapers, you are going to get a figure of many trillions (a few quadrillion?)

fun, and there's five cities of this size :smallannoyed:
oh well, i'm sure it can't be too bad, and maybe i could space out the skyscrapers more, so it's the same size, but with a less dense population?

[Jan Mattys]

i did choose it because it's the circumference of the earth (just the same as i used the diameter of earth, and the height of mt everest)

population of hundreds of billions? :smallconfused: i didnt think it'd get as high as that (although, it does go up as well, so i guess it's sort of like an earth sized tokyo..?)

With the population density of New York, all the world's current population could live in Texas.

I assume a city 40k Km wide could certainly host hundreds of billions. As for supporting them... that's entirely another matter. I'd say no, but with magic involved, anything could be possible.

Also, apart from teleporting devices, I think it's safe to assume that such a city wouldn't event behave as a city. For all purposes, a large part of the population would never leave its neighborhood. It's not a matter of being able to teleport... it's a matter that for all purposes in everyday life, the "other side of town" is as far and as alien as Australia is to Iceland, more or less. You could well have a couple dozen different climates spanning the city at any given time :D

[Waar]

Assuming a population density of ~40 000 per km^2 (which corresponds to the densest city on Earth, give or take) you would get a population of about 5*10^12 (5 trillion) (40 000*(12742/2)^2*pi) however the population density could be much higher, on account of the skyscrapers, on the other hand it could be much lower, with large uninhabited areas. (I can't give any info on wheter it could support itself, but in a fantasy/sci-fi setting sure why not, cities the size of planets are after all quite common in such works.)

[Somensjev]

i probably wouldnt have every single building by a sky scraper

let's say, the center, maybe a 742km diameter circle is all skyscrapers?

maybe every 1,000km from the center the buildings get 100m shorter (to a minimum 200), and it gets less dense?

(still a ridiculous population, but it's less?) i have no idea how to work out that population though

also, i was thinking that every floor in their buildings is 100m high, so even the tallest skyscrapers only have 88 floors? (so the center would be equal to 88 cities of an identical size?)

[Mastikator]

If the planet is covered in urban area, where is food grown?

If you can just magic up the food then a planetwide city would easily house thousands of trillions of people stacked line sardines on hundreds of levels spanning the entire planet.

If you can't just magic up the food then the city can't support itself.

[Somensjev]

the cities would probably have large farms on the outskirts who would sell their produce to large shops for consumption, the whole place isn't populated, there's easily more unpopulated area on each continent

think of it this way, each capital city, if this material plane was earth, would be smaller than hawaii, that's how i picture it

[supermonkeyjoe]

If there are items of at will teleport cheaply purchasable, why is the population so densely clustered? people could live pretty much anywhere on the plane and with a few teleport hops, be almost anywhere else

[Somensjev]

If there are items of at will teleport cheaply purchasable, why is the population so densely clustered? people could live pretty much anywhere on the plane and with a few teleport hops, be almost anywhere else

because they like big cities (they were smaller cities, then slowly developed over many years, until they became so large that you needed teleportation to get from one side to the other) and if your family lived in a city for 5 generations or more you'd find it hard to leave

[BWR]

Getting food will be a big problem without magic. Those living near the center of such places will probably never get fresh food of any sort without magic. Some of this might be mitigated with rooftop gardens, but not enough to feed everybody unless there's very low population density.
Of course with enough casters willing to cast Create Food and Water, or Tippyverse style Teleportation Circle economy and resetting traps of food creation, this will be easier.

What sort of jobs will these people have? Cities work because there are non-agrarian jobs that can best/only be done in large groups of people, but in historical times a much, much larger percentage of the population was engaged in agriculture than are today. If there is enough easy magic that most people don't need jobs and can lie around all day eating zzonga fruit, fine, but is this the case?

What about facilities? Water and sewage, most importantly. Water is covered under food, I suppose, but getting rid of the waste of this many people will be challenging.

[Slipperychicken]

earth sized tokyo..?)

So you're basically making Coruscant (http://starwars.wikia.com/wiki/Coruscant) and trying to keep it in medieval high fantasy.

The city (for lack of a better word) would probably be able to support itself using shenanigans like spamming Plant Growth (http://www.d20srd.org/srd/spells/plantGrowth.htm) in whatever farmland it actually has to have ludicrously-productive agriculture (no matter what, it'll need to import food if the people want to eat anything other than Create Food and Water gruel). Also, it would require truly epic infrastructure just to keep itself running from day to day, and extreme restraint to avoid exhausting every resource on the planet.

[Somensjev]

Getting food will be a big problem without magic. Those living near the center of such places will probably never get fresh food of any sort without magic. Some of this might be mitigated with rooftop gardens, but not enough to feed everybody unless there's very low population density.
Of course with enough casters willing to cast Create Food and Water, or Tippyverse style Teleportation Circle economy and resetting traps of food creation, this will be easier.

What sort of jobs will these people have? Cities work because there are non-agrarian jobs that can best/only be done in large groups of people, but in historical times a much, much larger percentage of the population was engaged in agriculture than are today. If there is enough easy magic that most people don't need jobs and can lie around all day eating zzonga fruit, fine, but is this the case?

What about facilities? Water and sewage, most importantly. Water is covered under food, I suppose, but getting rid of the waste of this many people will be challenging.

for the moment i have no idea about waste, but i'll think of something (or someone will have a suggestion)

for food, the cheap at will teleport items solve that (3000 gp for at will teleport)

water is rolled into food


as for jobs, i'm not sure yet, but a large percentage of them (i was thinking 25% or more) are full casters, of varying levels. there are large libraries, so there's lots of jobs with them (think of a small library as a building the size of detroit, and the height of everest)

there would be many clerical jobs open, and lots of demand for magic item shops, restaurants would probably see some requests too

[TheStranger]

for the moment i have no idea about waste, but i'll think of something (or someone will have a suggestion)

for food, the cheap at will teleport items solve that (3000 gp for at will teleport)

water is rolled into food


as for jobs, i'm not sure yet, but a large percentage of them (i was thinking 25% or more) are full casters, of varying levels. there are large libraries, so there's lots of jobs with them (think of a small library as a building the size of detroit, and the height of everest)

there would be many clerical jobs open, and lots of demand for magic item shops, restaurants would probably see some requests too

Easy waste disposal - sewers draining into a teleportation circle leading... elsewhere.

Easy plot hook - the residents of elsewhere have come to complain about this.

As for jobs, I think there's enough support work to be done to keep a big chunk of the population employed. Between clerical work, manual labor, service industries, etc., it at least passes the eyeball test. The logistics of how a city that size would function are staggering; you're going to have to handwave a lot of it.

[Somensjev]

Easy waste disposal - sewers draining into a teleportation circle leading... elsewhere.

Easy plot hook - the residents of elsewhere have come to complain about this.

As for jobs, I think there's enough support work to be done to keep a big chunk of the population employed. Between clerical work, manual labor, service industries, etc., it at least passes the eyeball test. The logistics of how a city that size would function are staggering; you're going to have to handwave a lot of it.

i figured i'd have to hand wave quite a bit, but i'm hoping to get it to at least be feasible (or even just believable)

i think a teleportation circle to the abyss would work..? :smallwink:

[TheStranger]

i figured i'd have to hand wave quite a bit, but i'm hoping to get it to at least be feasible (or even just believable)

i think a teleportation circle to the abyss would work..? :smallwink:
With magic, almost anything is feasible. If you're farming rather than just magically creating food, you need an arbitrarily large amount of farmland - figure 1-5 acres per person depending on how much magic you use (modern farming runs around 1 acre per person). So probably 10 times earth's surface area on the low end?

Then you set up a network of teleportation circles so that no farm is more than a day away from one. Do basic processing - butchering, milling, etc. - on the farm side, and teleport ready-to-use goods through. You can set up similar operations for non-food goods that you don't want to just magically create. Each teleportation circle feeds maybe a city block. So every block or so has a warehouse with a teleportation circle and a supermarket selling the food and other goods that come through. Or you can go every few blocks with bigger operations and multiple circles.

I can't imagine the governmental structure that would keep all this stable and functioning. Or it's all corporate. Either way, it's got to be a bureaucratic mess.

[Somensjev]

With magic, almost anything is feasible. If you're farming rather than just magically creating food, you need an arbitrarily large amount of farmland - figure 1-5 acres per person depending on how much magic you use (modern farming runs around 1 acre per person). So probably 10 times earth's surface area on the low end?

Then you set up a network of teleportation circles so that no farm is more than a day away from one. Do basic processing - butchering, milling, etc. - on the farm side, and teleport ready-to-use goods through. You can set up similar operations for non-food goods that you don't want to just magically create. Each teleportation circle feeds maybe a city block. So every block or so has a warehouse with a teleportation circle and a supermarket selling the food and other goods that come through. Or you can go every few blocks with bigger operations and multiple circles.

I can't imagine the governmental structure that would keep all this stable and functioning. Or it's all corporate. Either way, it's got to be a bureaucratic mess.

i was actually thinking of each city being a dictatorship, passed on by conquest, one guy gets to rule the whole city, first person to kill him becomes the next ruler, etc

as for farming, i'd probably have a lot less farms than that, but each of the farms use ridiculous amounts of magic to sustain, say 1000th of the city? (or less)

[Fouredged Sword]

One can't rule a population that big.

If you are lucky, you get to appoint the people who are in charge of the people who oversee the large organisations that monitor the smaller organisations that actually run things. Implementing any kind of change would be a matter of decades. Just sending out the news of a change would take months, just by shear numbers.

[Amano666]

One approach that has been used in Scifi and Fantasy before is to make the cities entities themselves. Perhaps conscious, and perhaps engineered or even grown organically, the cities would have waste elimination, distribution, and intake of raw materials handled via a series of "veins" and "arteries" like a living organism. Fires put out by excretion of water through the roof in automatically in response to the "pain" of burning "tissue". Perhaps even "eyes" everywhere that the police are able to use to track crimes. If you are hungry you could simply find a "teat" and the city itself would feed you. More people moving into the city? The city can just grow them rooms or even whole new blocks. Perhaps the residents can interface with the city or perhaps they forgot how, perhaps only some and it is up to the city to choose who.

[captpike]

honesty I think the best way to handle the government would be to have each block (or whatever), have its own goverment that handles food, police and everything it can. maybe even have different blocks have wildly different govements. like one is a monarchy, one a dictatorship, even some democracy's of various types.

above them you have the federal (cant think of a better name atm) goverment, they handle the military, and any problems between one block and another.

this also puts alot of plot hooks, intrigue between blocks, or between federal and blocks. being hired to get bad guys who cross block lines, something police cant do in some cases (not too long ago this was true of states in the US)

[TheStranger]

i was actually thinking of each city being a dictatorship, passed on by conquest, one guy gets to rule the whole city, first person to kill him becomes the next ruler, etc

as for farming, i'd probably have a lot less farms than that, but each of the farms use ridiculous amounts of magic to sustain, say 1000th of the city? (or less)
What does the ruler actually do? That doesn't sound like a tremendously stable system unless the ruler is just a figurehead and nobody cares anyway. Even if the ruler has some actual power, there's too much going on for one person to do anything hands-on - that would be like a single person ruling a few hundred Chinas. You need numerous intermediate layers for it to be remotely plausible.

Sociopolitically, your problem is that each city is roughly the size of all the land on earth, filled with roughly 100 times the earth's current population. It's hard to imagine anything that size functioning as a single unit. It's virtually impossible for a single person to "rule" something like that in a meaningful sense.

It's pretty much impossible for the farms to be smaller than the city, no matter how much magic you use. That's like growing all the food you need for a year (including raising livestock) in an area roughly the size of your hall closet. At that point, you're using so much magic that it's probably cheaper and easier to just abuse create food and water. Which is also a viable way to feed a city, and you could supplement it with smaller-scale agriculture.

I don't mean to ruin your fun, but the human brain doesn't handle scale very well. I think this is literally bigger than you can imagine. It's almost certainly large enough that any individual person would never visit more than a fraction of a fraction of the city. Let's say you can meaningfully experience a square kilometer of city a day (actually doing things in it, not just walking through and buying a postcard) - a person who spent their entire adult life roaming around the city would visit somewhere around .02% of the whole thing, and they wouldn't know any of that area particularly well. It would take something like 30,000 years to see the entire city. One person isn't ruling that unless they're immortal AND have millions (billions?) of people working under them. The farms to feed it are so incomprehensibly vast they might as well be infinite. The only way to begin to conceive of something on this scale is to start with a smaller unit - a city block, or a square kilometer - figure out how that works, and assume that there are an arbitrarily large number of comparable units in the city.

[captpike]

also cheap teleportation and the size and population of the city makes trying to find anyone who does not want to be found impossible, you rob a bank, teleport away (or use 5 or 6 teleportation circles) and you can never be found again.

it would mean you would have alot more jobs for the PCs though

[Tvtyrant]

Take Demon Lords from D&D. They rule supposedly infinite realms with tremendous populations of demons, and they mostly do it by not doing it. Demogorgon sits in a tower making magic items while dozens of exarchs rule the important areas for him, and the unimportant areas are just left to their own devices. That system only works because he is so canonically powerful that revolt against him has no hope of success, so everyone just does what they want while making sure not to raise any flags.

You could go all uncle Joe Stalin and have random killings of government officials to keep everyone paranoid and not sure who to trust so they follow orders to avoid drawing suspicion, but then you are destroying the pool of people whom can actually run things for you.

[Rhynn]

I don't mean to ruin your fun, but the human brain doesn't handle scale very well. I think this is literally bigger than you can imagine.

This so much. None of this makes any sense. The scale is beyond ridiculous. Sometimes you should just scrap a horrible idea rather than proceeding to grind it to the ground.

[Yora]

"No, that's too small. We have to right to... ludicrous size!"

[russdm]

i was actually thinking of each city being a dictatorship, passed on by conquest, one guy gets to rule the whole city, first person to kill him becomes the next ruler, etc


For a city you are talking, this kind of idea is essentially impossible. You would end up with nobody left alive if this is how it worked. Also, taking the city be conquest would be regularly wiping out a full quarter of the world' population every time with even more disappearing. Also, magical plagues become amazing weapons with the population density; it would only take a matter of days for most of city to be dead or dying or infected.

Cities this big would collapse under their own weight and with a government for each district/block would recent in frequent conflict, invasions into other districts/blocks and no central government could control it all without being seriously lawful evil. An empire like in Star Wars could control the cities but every other government would fit it nearly impossible. Crime would massively rampant and violence would be daily occurrence.

To be honest, No one would live willing in this kind of city. The size alone means having to thoroughly rely on magic, and anybody employing anti-magic auras can easily shut down large portions of it and wreck things. Its simply not feasible.

Now, if the cities are more the size of Hawaii than the earth itself, I can actually seeing it work. Otherwise you have to stick Darth Vader (or something like him) in charge of the city so it actually runs everyday. plus you need the massive civil workforce as well. If you can't do that, then the city won't ever run.

[captpike]

Now, if the cities are more the size of Hawaii than the earth itself, I can actually seeing it work. Otherwise you have to stick Darth Vader (or something like him) in charge of the city so it actually runs everyday. plus you need the massive civil workforce as well. If you can't do that, then the city won't ever run.

I think he said that as a reference to the relative size of the city to the plane it was on.

and I agree you have to have a government with very very tight reigns, and have a reason that people have to stay in the city, it would seriously suck to live there.

[Somensjev]

my idea for the government was sort of like this

dictator commands a group of people, each of those people commands a group, etc, etc, until you end up with the very last group of people, each of whom command a block or so (known as sectors, or something similar)

the dictator does have a large amount of say as to what happens, but, since the chain of command is pretty much chinese whispers on a grand scale, every sector ends up with very interesting interpretations of what the command actually meant

and the dictators would easily be in epic levels, so the only people who could usurp them would be another epic person

and by "conquest" i just meant killing them using any means necessary (straight up murder, assassination, honourable combat, etc)

it is most likely impossible to do this, but if there's even a remote chance to make this then i'm going to (of course, i can just handwave it all)


also, the living city idea doesn't seem too bad

[TheStranger]

More fun with scale, in the context of government. (By the way, I forgot a zero last time - it would take 300,000 years to visit the whole city, not 30,000)

Let's say for the sake of argument that the city is divided into sectors of approximately 10km square (100 square kilometers). There are roughly 1.3 million such sectors in the city. Each one has, as a conservative estimate, roughly 1 million people (total population: 1.3 trillion). Now let's say you take over as dictator and you want to get a feel for what's happening in the city. You ask each sector boss to send you a very brief report on their sector. Just a quick overview - something you can read in five minutes. You can read about 100 of these in a day, about 25,000 in a year. It will take you 52 years to read all the reports. Reading those 5-minute reports, getting even the broadest overview of what was happening in the city at a single point in time, is literally the work of a lifetime.

Simply walking along a single street from one side of the city to the other takes a year or more. In doing so, you're seeing an infinitesimal portion of the actual city. No matter where you go or what you do, you'll never see the whole thing in a hundred lifetimes. It is literally impossible for a person to keep abreast of current events in a meaningful way. For all intents and purposes, the city is infinitely large. Anybody capable of ruling it would be a deity by almost any definition of the word.

[Rhynn]

More fun with scale

Corollary: once you're condensing the information enough that one person can actually receive it, it's become meaninglessly broad. The person in charge of the city is, in fact, unable to know anything useful about enormous sections of it.

Imagine being in charge of the entire real world: you'd know so little about each individual part, you'd have no ability to make decisions about it. Indeed, you'd probably not even be able to make top-level decisions, except in a uselessly broad sense ("Feed the people" vs. "Don't feed the people"). This imaginary world is much worse.

[russdm]

That makes it sound like its not worth it to bother. Why rule when it takes you 52 years to know what is actually happening? You will need at least 100 or more people to read those reports and then report to you.

300,000 means an awful lot generations even for elves. If we give each elf about 300 years of life, it would take 1000 elven generations to make it from edge of the city to another. For humans with a max life span of 50 years, it will take 6000 generations to cross the city. It would take half of that to make it from the edge to the middle of the city. 500 generations for the elves and 3000 generations for the humans. This is all if started at point and where going straight across hitting/exploring every part of the city in the process.

You could have entire generations living and dying while only knowing a small part of the city and it would take even dragons a huge amount of time to fly around. Entire family lines would have to rule the city and bring plans to fruition. One ruler decides to build aqueducts throughout the city, it will take centuries for that to happen and will require every following ruler to stick to the plan to get done. Only creatures like dragons or gods or demons/devils have the necessary long term view to keep the city functioning or working really well. Mages don't have enough time unless they become liches.

I seriously think that the city needs to be shrunk down. It should take something like 52 days or hours to read all of the reports, not 52 years. With that kind of time requirements its completely impossible for anyone to actually rule the city. If a problem happens, the ruler won't find out until why past anything can be done. And employing a lot of public servants to help out, will only cut the time down but there is still the issue of delivering orders to all parts of the city.

Magic will have to be used in massive quantities to keep everything running. It only takes a few hundred plus casters using anti-magic auras to shut everything down. That's not a good way for a city to be setup like.

The cities are just way too big. It should 5-6 days max to cross some one side to another, maybe 10-11 days if you want it be seen from orbit. If you assume a walking pace of 20 miles an hour, then 8 hours of walking, that covers 160 miles, with 5 days of 8 hours of walking, you are looking at 800 miles for the city. It will of course take longer if walk slower, but at least this city is more manageable for a ruler, instead of 52 years or 300,000 years.

[Somensjev]

if the current size is too much, how large could i make the city, while it's still able to function?

i figured it'd be a long-shot for this to ever work, even with epic leaders

how big would it be necessary for there to be a ruler, who rules a small group of lesser-rulers? (having the main ruler aware of general issues, but not the more minor things)

[Rhynn]

how big would it be necessary for there to be a ruler, who rules a small group of lesser-rulers? (having the main ruler aware of general issues, but not the more minor things)

Corporations need that structure. Military units need that structure.

A decent estimate for managing people actively is a 50:1 ratio. Now, you're not actually managing your population, but rather the people providing government services, oppression, etc. - police, public workers and officials, etc. Let's say 10% of people are employed in the public sector. That means that...

For every 500 population, there's 50 public servants and 1 manager1.
For every 25,000 population, there's 2500 public servants and 50 manager1s, and 1 manager2.
For every 5,000,000 population, there's 500,000 public servants, 10,000 manager1s, 2,000 manager2s, 40 manager3s, and 1 manager4.
And so on.

I'd give an example with a trillion people (it's just division), but I don't know if we're talking short scale or long scale (there's a difference of 6 orders of magnitude).

Another kind of example: a "typical" (hah!) medieval realm is ruled by a king, to whom answer many direct vassals in his own lands, a load of officials (sheriffs, bailiffs, etc.), and so on. This keeps him and his chamberlains and stewards and marshalls pretty busy. "Beneath" the king are multiple dukes, each with a similar setup, often with personal lands comparable to, or even larger than, the king's. The dukes hold the fealty of many counts each, who hold the fealty of many barons, who hold the fealty of knights. These knights rule manors that control villages, and often have stewards or reeves in charge of a few villages.

That (extremely simplified) is 5-6 levels of delegation for realms that only had populations in the millions or tens of millions, and that set-up kept everyone quite busy.

[Toliudar]

You know what hasn't been discussed in this scenario? PC's.

These cities are so unknowably, bizarrely large that there's no way to develop a sense of identity for them. Unless the entire campaign takes place in one skyscraper - in which case, who cares about anything outside?

[TheStranger]

That's actually a harder question. I'd say that with liberal use of magic and trusted people to delegate* to, you could push it as high as 10-100 million people. Which puts you somewhere in the 20-40 kilometer diameter range. You could maybe go larger, but the larger you go, the less real control the ruler has over anything. At that scale, your ruler can have a meaningful impact, but he's still not dealing with everything hands-on - there are probably 4-5 layers of intermediaries at work, depending on how your government is structured.

*Of course, there's the fundamental question of why the ruler would ever delegate power to somebody with a clear interest in killing him.

Also, you should understand that your players will never see more than a tiny fraction of the city. Nor will you ever flesh out every neighborhood. Really, you're just looking at broad-brush boroughs, or large swaths of generic urban area. Somewhere between 100,000 and 1 million people, further increases in city size stop mattering much in terms of player experience. Beyond that point, bigger numbers only serve to convey to the players that it is a big city. (Which has some value - if your players live in New York or Tokyo, you'll never convince them that 100,000 people is a big city even if it has everything they'll ever need in-game.)

BTW, I didn't mean to say that an infinite city ruled by a god-mayor wasn't a viable campaign setting. If you imagine that the mayor's portfolio includes awareness of the city at a micro and macro level and the ability to manifest in multiple places at once to boss people around, and you assume that divine minds aren't bound by silly things like time and space, the setting actually works quite a bit better.

[Rhynn]

You know what hasn't been discussed in this scenario? PC's.

This is an excellent point. What is the purpose of these setting elements, and how will they be used in play? Coruscant was created for visuals, primarily.

[Waar]

Corporations need that structure. Military units need that structure.

A decent estimate for managing people actively is a 50:1 ratio. Now, you're not actually managing your population, but rather the people providing government services, oppression, etc. - police, public workers and officials, etc. Let's say 10% of people are employed in the public sector. That means that...

For every 500 population, there's 50 public servants and 1 manager1.
For every 25,000 population, there's 2500 public servants and 50 manager1s, and 1 manager2.
For every 5,000,000 population, there's 500,000 public servants, 10,000 manager1s, 2,000 manager2s, 40 manager3s, and 1 manager4.
And so on.

I'd give an example with a trillion people (it's just division), but I don't know if we're talking short scale or long scale (there's a difference of 6 orders of magnitude).


Using this method you would have 80000 4:th grade managers (each responsible for a population of about 62 million) for a population of 5*10^12 (aka 5 trillion) while the ruler would be a 7:th grade manager, however the bureaucracy would probably be quite a bit more, substantial, for it to do more than find and report problems. (each manager would probably have a small staff aswell)

edit: @op how much would a days "low-skill" work be worth in relation to that 3000 gp for at will teleport?

[Amano666]

Thinking about this in terms of how a society that we can relate to would cope with living in a supermega city the size of the entire planet earth is perhaps, respectfully, not the most effective means of envisioning the inner workings of such a city concept.

We can extrapolate numbers about population, how many police, how the taxes and garbage gets taken care of, but the problem is that there are no known actual cities on this scale, and for good reason. Our concepts of politics and economics can't cope with the density and logistics of the proposed mega city. The more we try to the more it starts to sound like a totally unfeasible idea for a campaign location.

Instead I might suggest that we look for the solution to this in the kind of organisms we see that do live in the highly structured societies that a supermega city would require. Ants come to mind.

First I would say that the prime material is not a likely location of such cities. Instead I would say that they are more likely to come about on planes strongly aligned to law. Only through the "natural" level of attention to detail and the clockwork like nature of a super lawful plane could a society in my mind come about that is able to handle the rigors of living in such density.

Second I would say that such a society would have to have a reason to stick together in the cities. Perhaps they have a religion based on the "queen ant" that binds them together for the common good, perhaps like ants they actually are all really related and so what they do is truly for the common good. Perhaps they are at war with the other "hives" and are bound against a common enemy.

I just don't see people as we know them living in such a place, but there is no rule that says the PCs have to be human. Dwarfs actually almost live this way except underground, imagine a super dwarf society that has carved out the entire inside of a planet, that would be about the equivalent size city.

[Fouredged Sword]

I would say you don't have a big city. You have a large nation made up of cities that all share borders. Each distribution zone would form the central point where a city's policy rules, and people form around these distribution points.

Food, water, raw materials, garbage disposal and government flow from these points (probably teleportation circles).

Look up tippy's points of light setting if you want more information about magic supercities in 3.5. His are not THAT big, but function in a fashion that if they shared a border, they wouldn't notice. You basically have a planet with all cities.

[russdm]

I would say you don't have a big city. You have a large nation made up of cities that all share borders. Each distribution zone would form the central point where a city's policy rules, and people form around these distribution points.

Food, water, raw materials, garbage disposal and government flow from these points (probably teleportation circles).

Look up tippy's points of light setting if you want more information about magic supercities in 3.5. His are not THAT big, but function in a fashion that if they shared a border, they wouldn't notice. You basically have a planet with all cities.

This actually sounds like the most workable solution. It is also completely believable.

[Another_Poet]

i probably wouldnt have every single building by a sky scraper

let's say, the center, maybe a 742km diameter circle is all skyscrapers?

Well, you're starting with a ridiculously huge city (which is kind of awesome) but you're trying to adjust it so it doesn't have a ridiculously huge population? Why?

Besides, even if you get it down to, say, 1 trillion instead of several trillion that is still... ridiculously huge :smallamused:


maybe every 1,000km from the center the buildings get 100m shorter (to a minimum 200), and it gets less dense?

In a single city, it makes sense to have an "downtown" area with the biggest buildings (though not all real cities have all their big buildings at the center). But a planet-sized city, which you said sprang up from many smaller cities, wouldn't have a single large center like this. There would be many regions of skyscrapers, many regions of hovels and tenements, and everything else.

I actually like your idea about a dictator who is often replaced by assassination or coup.

Note that instability like that wreaks havoc and your city is going to suck if that's how it's run. Bad sanitation... no meaningful law enforcement... constant armed rebellions... everything is unsafe (roads, buildings, bridges, wells) and unreliable (banks, transportation, clinics) and most large projects get done only through bribes or force. Local politicos or gangsters would hold much of the real power, and most people would be miserable.

That doesn't make it a bad setting. Sounds like a place that could use some heroes.


Corollary: once you're condensing the information enough that one person can actually receive it, it's become meaninglessly broad. The person in charge of the city is, in fact, unable to know anything useful about enormous sections of it.

Imagine being in charge of the entire real world: you'd know so little about each individual part, you'd have no ability to make decisions about it. Indeed, you'd probably not even be able to make top-level decisions, except in a uselessly broad sense ("Feed the people" vs. "Don't feed the people").

^^ don't listen to this argument. Design your city-world with one executive authority if you want, then figure out how they make that work.

In the real world we have nations with huge large land area (Russia) and population (China) and central top-level authorities still make meaningful, informed decisions. We manage this largely because of our communication technologies, but you have magic for that. Forget teleportation; continuous-use Sending items have you covered.

Bear in mind that globe-spanning empires were managed in the real world by the 1700s (albeit with poor oversight), and they were relying on the speed of sail-powered boats to pass information. The Romans did it with beacons and fast runners. Even without magic your city governance is viable.

(Of course, effective governance would require lots of structure, which your corrupt dictatorship would likely lack. Ideally you'd have local, provincial, and large-regional levels of government, who administer their local areas and report up the chain, as well as a large legistlative body or at least advisory council at the city-wide level in addition to the executive.)

I do want to say one thing about the teleport spells. I don't think they should be cheap, for three reasons.


Even if people really want them, the mages who make them have overhead and want to be paid for their time/expertise. They can't just waive these costs.
Most people have no reason to go outside their home district.
Those people who do want to travel (for business, to learn about other provincial cultures, etc) create a niche demand. Wizards stand to make big profit by charging them accordingly, and have no incentive not to.


I would imagine the government controls most of the teleportation, and makes it available as fixed portals at local stations, if that.

Besides, if cheap teleportation is available how did your city not become this place (http://www.giantitp.com/forums/showthread.php?t=222007)?

[Somensjev]

-very useful stuff-

ok, firstly, for the population, i don't really care too much how large the population gets, it would be awesome if the whole city was skyscrapers everywhere, but it'd probably be less realistic (that's a strange thing to talk about when describing a city with the same circumference as our planet)

also, for the leader, anyone could become the leader, and most of the population wouldn't even care, it wouldn't change how the city was run that much, the leaders can only decide on very general things, and they have to quickly learn to be very specific when issuing orders (such as, demanding that a waste system is invented, anything could happen in any given sector)

and as for how the general populace reacts to the dictatorial power exchanging is kind of like this "oh, some random homeless guy of the street killed out leader? well good for him" or maybe "oh, some random god descended from the heavens and smote our leader? well that's pretty interesting" bottom line is, it doesn't affect them that much

[nedz]

Assuming that a city this large would collapse under it's own inertia (I'm not totally convinced by that — however, for the sake of argument...) you could set the campaign some time after the collapse. You would then have a world of ruins, with people grazing sheep amongst the old skyscrapers. It might be easier to manage the game and it would be more personal.

[Rhynn]

I guess a campaign in such a setting could work out something like Blame! (http://en.wikipedia.org/wiki/Blame!), where the PCs wander from location to location (sans any kind of teleportation) looking for some elusive goal, meeting wildly different communities all within the same "expanded megastructure" (the city), with only the vaguest idea of where they even are (as most people probably would have, the city being too large for one person to see or really comprehend; and no one having any experience of something that isn't the city). It could have dimensions of an ontological mystery, trying to figure out what the world even is...

[Another_Poet]

I like Rhynn's idea. I'm getting a very (http://www.youtube.com/watch?v=mu1iND6vtcE) Brazil feel (http://www.youtube.com/watch?v=teufz17PqoY) off this setting.


also, for the leader, anyone could become the leader, and most of the population wouldn't even care, it wouldn't change how the city was run that much, the leaders can only decide on very general things, and they have to quickly learn to be very specific when issuing orders (such as, demanding that a waste system is invented, anything could happen in any given sector)

and as for how the general populace reacts to the dictatorial power exchanging is kind of like this "oh, some random homeless guy of the street killed out leader? well good for him" or maybe "oh, some random god descended from the heavens and smote our leader? well that's pretty interesting" bottom line is, it doesn't affect them that much

So why does anyone want to be the leader?

I mean it sounds like the job description is:


You get no significant power
You get no significant respect
You are likely to be assassinated


The only explanation I can imagine is that the Dictator is a sideshow. Some group of elite regularly send in a new dictator to kill the old one and live like a king for a couple years, maybe issue a few edicts, to distract the masses. Meanwhile the elite run everything from behind the scenes.

But even that doesn't work too well, if no one cares who the leader is or what they say. I mean it's not much a sideshow if no one's watching, right?

[Kelb_Panthera]

The logistics of this are utterly staggering. The amount of food necessary to feed enough people to actually build such large cities will take up enormous tracts of land and couldn't reasonably be transported non-magically to the inner city at all.

Simply put, there will be nothing pseudo-medieval about it. The technology level that evokes that feel is simply not up to the task of supporting a city that's more than a few miles in diameter. You're talking about a city that would cover a quarter of the planet earth. Magictech will be the order of the day. Even with teleportation circles the distribution would necessitate magical food transportation at the very least. Governments would have to look more like modern bureaucracies except even moreso and communications of anything less than modern speed would be simply untenable for such a massive organization. About the only medievalish thing about it is that people will still be killing each other primarily with bladed weapons rather than projectiles, the cost of magical projectile devices being prohibitively expensive.

The ecology of such a place is difficult to guess at since it requires a planet much more massive than earth an ecology is so dependent on meteorology and they, in turn, are both dependent on geography.

As world building exercises go, you've picked a doozy.

[vhfforever]

It sounds like you're generating Mega-Cities (ala Judge Dredd) and having them all grow together. And, I think if you're intent on keeping them the scale you've mentioned, treating it in that manner would be the best solution. Large blocks or fantasy-equivalent arcologies (Shadowrun-ish) that are each independently run by a group, who then report back to a greater power higher up the chain.

This way, you only have a few hundred (or thousand) 'zones' within the city, each independent in the term of monitoring itself for law and the like, reporting back to their Overlord (or whatever you want to call it) who keeps them all alive out of the kindness of his heart.

[Fouredged Sword]

See, I think that large sections of the food and water issue can be resolved through create water traps. You don't need distribution if every tower is self sufficient. With water comes sanitation, food, and energy. Once you have those, you have the foundation of a society.

See, the reason that the city is built on the tower design is because that is the design that allowed for the city in the first place. Water on a tower makes for a really good source of power.

The tower has several levels that create sectors. The very top of the tower has a large basin and curved pipe that extends down the center of the building. The basin is constantly filled with traps of create water. These traps create 6 gallons of water a second. 10 or so of them exist on the top of every tower.

This provides massive amounts of running water for the rich population who lives on the top of the tower. Under them it powers the machines of industry that dominate the middle tower. Under that is the lower level housing.

More importantly, when the water passes under the tower and into the underdark it flows into massive friction engines to generate heat. The then hot water is pumped into fields of thermovoric fungus that is grown for sustenance. Most of the population eats this fungus for three meals a day, and the lowest level worker are those who labor in the damp dark farm caves. Surface plants are a treat for the middle class and a staple only for the rich who can afford rooftop gardens.

At 40/gal a second you are looking at generating enough energy to make modern energy generation green with envy. Even if you stuck to inefficient means of harnessing the energy like water wheels or crude turbines, you would still have the energy to power a modern industry.

It's a culture that never generated steam energy though. Coal would be too expensive. The tower is warmed with water friction generators (two hardened stone blocks rubbing together, driven by a water wheel). Everburning torches are used for light. Metal flows from mines cut using hydrolic pressure and man power. Prestidination is used to clean and sanitize the tower city.

Because much of the tower is dedicated to industry, it's population density is not the highest. Each tower supports several hundred individuals. It would also be wider than a normal tower in the modern world, likely several city blocks wide. It would be made from any convenient material, as hardening though magic allows for any material to be made far stronger than steel. Wood, stone, and soft metals like copper and tin are all used.

Around the base of the tower is farmland and industry that wouldn't in a tower well, like metallurgy. Each tower supports maybe 1000 people in total. Towers are within sight of the next tower, with a sprawling farm, tenement, and industry that flows from one to the next.

I call it a water-punk setting. Psudo modern tech based on the waterwheel and magic. It is a damp cold setting, where you must have the grit to survive the ever lasting grind of water on stone.

[Driderman]

I like Rhynn's idea. I'm getting a very (http://www.youtube.com/watch?v=mu1iND6vtcE) Brazil feel (http://www.youtube.com/watch?v=teufz17PqoY) off this setting.



So why does anyone want to be the leader?

I mean it sounds like the job description is:


You get no significant power
You get no significant respect
You are likely to be assassinated


The only explanation I can imagine is that the Dictator is a sideshow. Some group of elite regularly send in a new dictator to kill the old one and live like a king for a couple years, maybe issue a few edicts, to distract the masses. Meanwhile the elite run everything from behind the scenes.

But even that doesn't work too well, if no one cares who the leader is or what they say. I mean it's not much a sideshow if no one's watching, right?

Perhaps the role of the Dictator is held up as the ultimate goal by said shadowy elite. Basically, every citizen, it is said, can become Dictator or one of his hangarounds and be relieved from their daily grind to live a life of respect and luxury, surrounded by almost equally pretigious hang-arounds. The Dictator and his "court" is not so much a ruling courte as the ultimate celebrity show and all the citizens of Giant Crazy Mega City want to sit on that Golden Throne or at least bask in it's presence. To this end, competitions, lotteries and such are held to decide who will be uplifted to this illustrious life, all duly narrated, commented on and exposed to the masses of Giant Crazy Mega City through various magical methods.

All the while, the shadowy elite ensure sure the gears of Giant Crazy Mega City keeps turning for their nebulous purposes...

[Rhynn]

The logistics of this are utterly staggering. The amount of food necessary to feed enough people to actually build such large cities will take up enormous tracts of land and couldn't reasonably be transported non-magically to the inner city at all.

Good point: for planet-sized cities, we're talking about dismantling planets or stars for building materials... and there's several of them around. Of course, if they're on a planet large enough to contain them - we'll not speculate on the physical effects of that - the materials might have come from the planet, by means of magic.

[Xelbiuj]

I love the idea of a Mega City.
Running it doesn't seem like it would be THAT difficult.
Layers of bureaucracy and self management will handle most things. Of course there would be an absurd amount of crime but it's not like the "King" needs to micromanage everything.

As for getting "news out", a simple (yet expansive) system of sending would do fine. Exponential growth.
One Sends to two, 2 to 4, to 8 to 16. Etc, at 10 minutes a cast it's not like it would take more than a day to get the word out to a million plus sectors.

I like thinking about the massive infrastructure that would be involved. Sewer canyons, moving trillions of gallons of waste, eventually to a gate connected to some lower plane, where possibly unbeknownst to the city dwellers, some demon lord is using this new cesspool to spawn vile demons.

There would be no room for grave yards, just crematoria and the horror that comes from burning putrid flesh and preparing . . . recycling the still good flesh of 10's of thousands of corpses for later consumption. Soylent Green is people!

And of course, Paladins as Judge Dredd style judges.

[Another_Poet]

Good point: for planet-sized cities, we're talking about dismantling planets or stars for building materials...

Or Fabricate. The OP has already said there's teleportation everywhere, might as well go the whole 9.

[Rhynn]

Or Fabricate. The OP has already said there's teleportation everywhere, might as well go the whole 9.

Fabricate just transmutes material; true creation is required, but that only creates 1 cu. ft. per caster level per casting, and is an 8th-level spell...

[Zero grim]

Ive tackled making mega-cities recently and i manged to get a 30 mile radius city (centered in a 300 radius farmland to feed it) working rather smoothly, most of the problems are resolved due to very good semi-magic sewers and a very fast and powerful breed of horses.

I bring this up to bring the main problem my players had with the setting was that they never cared for it, a city of that size with a massive population and army the viewed as being basically beyond any real threat, even massive kingdoms of didn't look like a challenge to defend against so they never had any real motive to be interested in anything.

When you have 1 million guards a small percentage of them are likely high level characters that probably could solve any issue the PC's have been called in to deal with.

another problem I've run into is figuring out how and why the city came to be, your city's are basically planes of existence all to themselves so you need to ask why were they made to be so huge, do they need the space for population and if they do the players will feel like a few drops in the ocean against the trillions of npc's that could replace them.

As for feeding your city, i can see two options:

Magic OR every house has food that can be grown there, like a fungus that grows from the bricks.

[nedz]

I could see something like Nessus working. That's the city in the Book of the New Sun. Nessus is Ancient and Huge though not planet sized. The trick with cities is to give them character, which is hard to do on that scale. You could break it down into the neighbourhoods in which the game actually occurs, but then it's not a huge city but a town amongst town — though most real large cities work like that anyway.

[Kelb_Panthera]

Fabricate just transmutes material; true creation is required, but that only creates 1 cu. ft. per caster level per casting, and is an 8th-level spell...

While that really ought to be true, there's a glitch in the rules that makes a fabricate trap or item produce real material from nothing.

[NikitaDarkstar]

So here's my thoughts on this. First of all I have to say that I do consider the general idea pretty damn awesome, even if it is more of a Sci-FI trope.

Teleporting. In a city this big Teleporting would logically be fairly restricted. Why? Multiple reasons:
1) Teleporting can fail. You don't want a random dude accidentally teleporting himself into the wall halfway up a sky-scraper and causing structural damage.
2) It's to easy for criminals to get away.
3) It's to easy for assassins to get in.
No, teleport at-will items would be something government officials (law enforcement, etc.) has access to, and it would be on file who has access to it, and losing such an item (or possessing one unlawfully) would be a quite severe crime. The common people would most likely have access to a teleport-gate network instead (are you familiar with Stargate? Think that. Big devide where you "dial-up" your destination, step through, and arrive at the other end). It would be maintained and operated by the government, but most likely cheap/free to use (think modern public transportation fees at the most.)

The ruler, as I see it you have two options here. The first is a regular mortal that can be killed (or kill) with enough skill that can take the job. The upside there is assassination plots are fun. The downside? Realistically he'd be a puppet simply due to the sheer size of the city.
Option two. Are you familiar with The Lady of Pain? If not, read up on her. She's the Immortal, seemingly all-knowing, most-likely deity, ruler of the city Sigil (powerful enough to keep gods out). The upside here is that she does know everything that goes on in her city, she's just fairly off-hands. Downside? It takes some of the fun out of it.
Option 3 (sort off) in my opinion would be to combine the two. Anyone who can take the city gains through whatever means (maybe the city itself bestows it?) the power to be aware of what happens in the city at all times, make informed decisions (if one so chooses) about the city on any level, and enough power to protect it from threats. That just happens to amount to near god-like powers. But if you can take down the current leader? Knock yourself out. Cool sounding title, optional.

Food.
It seems to me that it may not be completely necessary to have farms outside the city. You could have them under the city. Sewer waste does make rather good fertilizer, fungus grows well in dark, damp areas, and with the assistance of some daylight spells you could grow quite a bit down there. You could even raise subterranean critters for cattle.

Classes/Casts/Rich/Poor
Now this may be my love for dystopian settings showing, but it seems to me that a setting like this would have some rather big differences between the social classes and the rich and the poor. Imports from outside the city would most likely be fairly expensive, meaning finer meats, certain fish, certain fruits and vegetables etc. would be a luxury item. It also seems like government workers would basically be the nobility, and the higher up in the pecking order you are, the more "noble" you are, with access to higher pay, better apartments (lets face it, it would be far more desirable to live at the top of a skyscraper than the bottom, especially if you can manage to make the roof private and part of that apartment!), be in a position to have certain outside items brought in and so on.
On the flip end the poor would be pretty damn poor, and there'd probably be quite a few of them. Basically the "city farmers" worst regarded people out there (never mind the fact that they're doing important work, growing food inside the city would be yucky).
You'd also need an extreme amount of saftey and emergency workers. Builders to maintain buildings, firefighters (magical or otherwise) in case of fires, a very large police force to keep the peace etc. But you will need A LOT of various engineers, maintaining buildings and infrastructure would be paramount.

And last, you need a good reason why people decided to cram into large cities in the first place, and stay there. Is the outside world really that dangerous? What happened?

[Somensjev]

So here's my thoughts on this. First of all I have to say that I do consider the general idea pretty damn awesome, even if it is more of a Sci-FI trope.

Teleporting. In a city this big Teleporting would logically be fairly restricted. Why? Multiple reasons:
1) Teleporting can fail. You don't want a random dude accidentally teleporting himself into the wall halfway up a sky-scraper and causing structural damage.
the at will items can't fail
2) It's to easy for criminals to get away.
there are records of who gets a teleportation item, they can not be passed to others, and they track where you teleport to
3) It's to easy for assassins to get in.
it's just as cheap to get a location protected from teleportation
No, teleport at-will items would be something government officials (law enforcement, etc.) has access to, and it would be on file who has access to it, and losing such an item (or possessing one unlawfully) would be a quite severe crime. The common people would most likely have access to a teleport-gate network instead (are you familiar with Stargate? Think that. Big devide where you "dial-up" your destination, step through, and arrive at the other end). It would be maintained and operated by the government, but most likely cheap/free to use (think modern public transportation fees at the most.)
the stargate-like teleport item might be useful, i'll have to consider that

The ruler, as I see it you have two options here. The first is a regular mortal that can be killed (or kill) with enough skill that can take the job. The upside there is assassination plots are fun. The downside? Realistically he'd be a puppet simply due to the sheer size of the city.
Option two. Are you familiar with The Lady of Pain? If not, read up on her. She's the Immortal, seemingly all-knowing, most-likely deity, ruler of the city Sigil (powerful enough to keep gods out). The upside here is that she does know everything that goes on in her city, she's just fairly off-hands. Downside? It takes some of the fun out of it.
Option 3 (sort off) in my opinion would be to combine the two. Anyone who can take the city gains through whatever means (maybe the city itself bestows it?) the power to be aware of what happens in the city at all times, make informed decisions (if one so chooses) about the city on any level, and enough power to protect it from threats. That just happens to amount to near god-like powers. But if you can take down the current leader? Knock yourself out. Cool sounding title, optional.
i'd probably go with the first one, but the last one wouldnt be too bad

Food.
It seems to me that it may not be completely necessary to have farms outside the city. You could have them under the city. Sewer waste does make rather good fertilizer, fungus grows well in dark, damp areas, and with the assistance of some daylight spells you could grow quite a bit down there. You could even raise subterranean critters for cattle.
i was thinking rooftop gardens, but underground farms works just as well, and why not have both

Classes/Casts/Rich/Poor
Now this may be my love for dystopian on an unrelated note, the five cities are called; Tartaros, Duat, Annwn, Naraka, and dystopia settings showing, but it seems to me that a setting like this would have some rather big differences between the social classes and the rich and the poor. Imports from outside the city would most likely be fairly expensive, meaning finer meats, certain fish, certain fruits and vegetables etc. would be a luxury item. It also seems like government workers would basically be the nobility, and the higher up in the pecking order you are, the more "noble" you are, with access to higher pay, better apartments (lets face it, it would be far more desirable to live at the top of a skyscraper than the bottom, especially if you can manage to make the roof private and part of that apartment!), be in a position to have certain outside items brought in and so on. actually, my cities are more like ancient greek in that respect, the higher up you are the poorer you are, since higher floors take longer to get to, and if there's a fire you take longer to get to the ground (mitigated with teleporting elevators) however, if you cant get to the elevator and there's an emergency you're more at risk
On the flip end the poor would be pretty damn poor, and there'd probably be quite a few of them. Basically the "city farmers" worst regarded people out there (never mind the fact that they're doing important work, growing food inside the city would be yucky). the farmers are highly respected, they feed a large amount of people, and they put their lives on the line doing it, there are almost epic level people who spend half their lives protecting those farms
You'd also need an extreme amount of saftey and emergency workers. Builders to maintain buildings, firefighters (magical or otherwise) in case of fires, a very large police force to keep the peace etc. But you will need A LOT of various engineers, maintaining buildings and infrastructure would be paramount.

And last, you need a good reason why people decided to cram into large cities in the first place, and stay there. Is the outside world really that dangerous? What happened? the outside world is densly populate with various powerful creatures, and is also often visited by demons and devils, so humanoids quickly had to join together in large groups to survive

answers spread throughout the text, hopefully that helps understand it more

[TheStranger]

On the topic of sewer farms: you can't beat entropy. Yes, fungus will grow underground using nutrients from surface waste. The fungus will capture only a relatively small portion of the energy in the waste. When that fungus is eaten, only a small portion of the energy in the fungus will be returned to the sewers. It's not remotely close to a sustainable cycle without a constant outside input. Magic may work, but make sure it's explicit, because this would bug me as a player (it bugged me about the Matrix, too).

Also, there are legitimate and serious health concerns with growing food using human waste as fertilizer (completely aside from it being disgusting). The primary one being that it's full of microbes that humans are susceptible to. It has to be processed pretty heavily to remove that as an issue, which takes up more space.

Finally, a thought on structural engineering. When you have mile-high skyscrapers, material strength becomes a serious problem. Whatever you're making your building out of, the bottom has to support the weight of the whole thing. Stone won't cut it. At that scale, I don't think steel will either. Essentially, you'd have to build the entire city out of adamantine or some other form of unobtainium.

[Fouredged Sword]

The spell harden could solve many of the structural problems. One can make bamboo have the hardness of steel, or paper. Steel becomes poor mans adamantine with a hardness of 20.

Also there is a RAW argument that it stacks with itself allowing NI hardness on materials.

A self resetting hardness trap could be used as a hyper efficient treating oven where metal is turns into super materials.

[NikitaDarkstar]

The Stranger, I'm not saying you're wrong, you're not. But lets face it, we're playing with the thought of cities as large as the planet being run with magic, so at this point it's more along the lines of "does it sound plausible at first glance in a fantasy setting with magic?" rather than "Would it actually work?".

For example, I could totally, in a fantasy setting, see a mountain having been turned into a massive skyscraper over the years. It's is actually possible, or even practical? Heck no. Would it break my suspension of disbelief? Nope.

Granted, what breaks your suspension of disbelief tends to be very personal, and tied to how much you know about the subject. An architect may laugh at the mountain-turned-skyscraper but not bat an eye at the weird mechanical shenanigans going on in Eberron. Meanwhile I as a mechanic keeps wanting to pick it a part to see how it works and just get "it's magic" slapped in my face, which totally messed with my suspension of disbelief.

[TheStranger]

For me, it's important that the setting acknowledge the things that only work because of magic. Something like the self-sustaining sewer farms will jump out at me and drive me crazy. The implausible skyscrapers less so.

As you say, it's a very subjective thing. To use your example of the mechanical stuff in Eberron, though, think how much worse it would be if it wasn't magic and there was no way it could possibly work.