Designing Atlantis

[EscherEnigma]

Howdy, looking to get a campaign started soon, and I'm hoping for some help in fleshing out the city that'll play a major role in the first planned arc of the campaign.

Campaign Concept: "Earth", but with D&D stuff thrown in. The campaign will start in ancient history and then jump forward in time to interesting points to explore specific ideas.

City Concept: Set in the Ancient World (6000 - 9000 BCE, I plan to keep it vague), Atlantis is an "advanced" city, ruled by elves with a subservient human class.

What I've Already Got
Where it is: For plot reasons, Atlantis is in where the Mediterranean Sea will be. Once it's let back in. At the time of the story it'll be in a much smaller sea surrounded by vast Mediterranean Sea-shaped salt flats.

Who lives there: Elves and humans. I want the elves to be out-numbered by the humans, but I'm not sure on the ratio. The idea being that the elves are educated, magically powerful, and well equipped, and so they're able to keep the magically and technologically and educationally deficient humans in check. I'm not sure how far that ratio can reasonably be pushed however. I expect the total population to be in the thousands, with 10,000 as the upper limit.

General Feel: My main exposure to the idea/myth of Atlantis is Plato, so I'm planning on giving it a Greek Roman vibe, but with magical engineering vs. mundane engineering. So the city's population will get their water via a network of Decanters of Endless Water (or similar magic), their gardens and farms will be grown with the aid of magic, and the elves will carry about on elegant arches and bridges suspended in air with Immovable Rods and so-on. The humans, meanwhile, will probably have dirt huts in the outer ring or some-such.

What I'm Looking for Help With
In short, I have the (very) broad stroke of the city, including the central conflict that the players will be thrust into. What I'm missing and need help with is fleshing out the details of the city such that when the PCs go off in an unexpected direction, I have a general idea of what's over there. So I guess what I'm hoping for is questions to help refine those broad strokes a bit, though I have no expectation (or indeed, desire) to produce a finished masterpiece.

And on that note, if there's a standard list of "questions you should answer about your fantasy city", that'd be greatly appreciated. 'cause each time this campaign advances in time I'm gonna have to do this again.

Thanks for any help,
EscherEnigma

[VoxRationis]

The "oppressed slave class" trope in fantasy has a lot of resonance with the real world, but if they have things like immovable rods and decanters of endless water commonly enough to incorporate into their infrastructure and architecture, why do they actually need a slave class? They clearly have the magic to accomplish the same goals more cheaply and with no chance of rebellion. 99% of the things a slave could do you could do with unseen servant; most of the rest would work with an animated object or some other magical item, or just with an educated white-collar clerk for the mental tasks. Possible explanations include that it's a display of wealth (sure, a slave is useless and an expensive liability, but I can afford a dozen anyway) or a holdover from a time when magic wasn't as common (in which case I'd expect to see elves questioning the necessity of the practice, which would make for an interesting central conflict).

Even if the humans are just "subservient" without being slaves proper, the question still applies.

[EscherEnigma]

Crunched the numbers, and unless I'm missing something, it looks like it'd only take one Decanter of Endless Water, going 24/7, to supply all the water needs of a population of 6000 people that don't have modern standards of cleanliness. Throw in two more for redundancy and to allow this city to be absolutely horridly wasteful with water and not rely on rain or natural water sources for agriculture either.

Immovable Rods in architecture... I still like the idea, but I think it'll probably be reserved for the most important/wealthiest, rather then a regular thing.

So not as much magic as I originally thought.

As for why you need a large underclass: agriculture. As I'm stating out the city, it's got about 5000 humans and 1000 elves (like I said, small by most standards, huge by Stone Age standards), most of the humans are going to be working in agriculture, with the remainder acting as servants/cleaners/muck-ruckers and so-on, allowing the remaining sixth of the population to have their comfortable upper-class lifestyles. To the best of my knowledge there isn't really any animated object/golem/etc. that could effectively be a farmer that's even close to the "price" of a couple of human peasents/serfs/etc. that pay you for the privilege of farming the land. That is to say... just like in the real world, automation has the possibility to replace workers, but it isn't often economically feasible, even if magical AI is leagues ahead of real-world AI.

________
†Assumptions: Using a Decanter of Endless Water as a principal water supply necessitates that it's tweaked so as not to need constant activation. So a Decanter, going full geyser mode, pumps out 30 gallons of water in six seconds, or 300 gallons/minute, 18,000 gallons/hour and 432,000 gallons/day.
Modern water needs are about 80 - 100 gallons of water per person per day (not counting for efficiencies from multiple people in the same household). A large chunk of that is for hygiene and cleanliness, so our Ancient Era city probably spends less per person. But let's say our city uses that same amount, that one Decanter can support 4,320 people. If even half the water is used, then it can support over 8000 people.

[avr]

There was a little long distance trade even that far back. Ornaments mainly (the first copper was used for decoration or maybe ritual rather than tools or war), booze, a little raw materials (unusual stone certainly) for high status items. Does Atlantis fit into that?

It sounds like the sea could be prone to varying its level quite a bit in dry years or wet. Or over decades as part of a natural cycle. Unless of course the elves have the magic to stabilise that.

Agriculture is effective at feeding a population which has reached maximum density for hunting/gathering, but full on peasantry has the problem that it's pretty easy to leave and go hunting/gathering somewhere else at this time. Maybe the elves have magical control over the surrounding sea?

[VoxRationis]

I think most of the 80-100 gallon measurement comes from the use of water in manufacturing and agriculture...

[Balyano]

There was a little long distance trade even that far back. Ornaments mainly (the first copper was used for decoration or maybe ritual rather than tools or war), booze, a little raw materials (unusual stone certainly) for high status items. Does Atlantis fit into that?

It sounds like the sea could be prone to varying its level quite a bit in dry years or wet. Or over decades as part of a natural cycle. Unless of course the elves have the magic to stabilise that.

Agriculture is effective at feeding a population which has reached maximum density for hunting/gathering, but full on peasantry has the problem that it's pretty easy to leave and go hunting/gathering somewhere else at this time. Maybe the elves have magical control over the surrounding sea?

Given that this takes place at the bottom of an emptied out Mediterranean basin it may be too hot and dry to try and leave.

Atlantis would probably be at a higher elevation than the surrounding salt flats. Anyone trying to leave has to cross those salt flats. Thats temperatures at the bottom of that basin would be fatal. The lack of water would be fatal. The only water available over much of the basin would be hypersaline....so fatal. Only where rivers flow into the basin, and on the highland areas, many of which would become islands as the basin floods, are livable.

Maybe Atlantis is cut off, or maybe its a livable highland region next to or inside one of the hypersaline seas in the basin. If you get on a boat you can travel to the most distant part of the sea where a river flows in, maybe the Nile. If you follow the river you can reach the outside. If you are a poor peasant you have no way to get a boat to reach the river to reach the outside.

This keeps the serfs from abandoning the farms to hunt. There is nothing to hunt because there are no wild lands. Just sweltering dry desert. All trade come across boats, that's the only way in or out, and the elves control the boats.

[Dusk Raven]

If the area surrounding Atlantis is that deadly (do salt plains in particular get hotter than normal deserts or something?) I have to wonder how the hell they even made it there to settle the place, or why, at least in the short term.

Also, a note about slaves - slavery in a society tends to seriously retard their technological growth. There's not really any point in labor-saving machines, for instance, if you just have slaves do it anyway. At most, efficiency technologies will only be pursued if you can get more output with the same amount of slaves. Then again I think that's how labor-"saving" tech works today, but even so, since muscle power is in supply there won't be much demand to assist it, much less replace it. For instance, the Ancient Greeks at one point had the concept of a steam engine down, but they never used that knowledge for anything other than little rich philosopher's toys. Granted there were likely quite a few other things stopping them from making a steam engine, but the point is there's not much of a desire to fix what wasn't broken, at least from the slaveowner's perspective.

[avr]

If the salt plains are too hot for travel, wait for winter. If they're trackless, follow one of the millions of rivers draining into the Mediterranean basin; some may peter out in the salt flats but I think more than the Nile would reach the smaller sea mentioned. If Atlantis is surrounded by a very saline sea, build canoes (possibly dugouts) which should float very easily in the salt-rich waters. None of these is beyond stone age technology and understanding.

Which is why I wondered if the elves perhaps had magical control over the sea.

[Balyano]

If the area surrounding Atlantis is that deadly (do salt plains in particular get hotter than normal deserts or something?) I have to wonder how the hell they even made it there to settle the place, or why, at least in the short term.

The reason it is so hot has to do with the area being so far below sea level. The adiabatic lapse rate means that on average it would be about 18 f, or 10 c hotter than a nearby continental region like central iraq would be. In the deeper parts it would be about 60 f, or 33 c hotter than iraq. This combined with the dryness dehydration and heat stroke would be a big problem. I would assume the areas near water would be cooler, but probably muggy.

There are two ways to reach the place that come to mind. One is to follow the rivers until you find the sea. Another longer term way is how elephants, hippos, and hyenas made their way to places like malta. As the sea dried it would first leave behind swamps and grasslands that the animals could inhabit, eventually reaching the highland regions. Then as the sea continued to shrink and moisture became more scarce the surround lowland regions became dessert. Eventually you end up with an island of life surrounded by desert.

Walking around the sea might not be viable, if most of the sea is surrounded entirely by low lands then the travel is a still a hot road with no fresh water. The idea is that the habitable highland region is bordered by the sea and the salt flats. The sea is surrounded by salt flats except the part next to the highland region and the river delta opposite the highlands.


Years ago I had a similar idea for a setting, but instead of a dry mediterranean it was a dry arctic ocean. Though I added himilaya height mountains to ring it to keep clouds in/out to keep the amount of water in the basin stable. Much would evaporate and form an ever thickening cloud layer all summer. Then in fall it would begin to rain out as a torrent. Then six months of night as everything slowly froze. Except around the hotsprings, which would have been undersea vents in real life.

[Xalyz]

An artificial oasis in the middle of a salt flat would be a great defense against invaders. Maybe seasonal flooding brings trade to the city and strands new commoners as the tide is unpredictable.

[EscherEnigma]

I think most of the 80-100 gallon measurement comes from the use of water in manufacturing and agriculture...
What I used for my numbers (http://water.usgs.gov/edu/qa-home-percapita.html). Manufacturing and agriculture are accounted for separately.

@Balayno
That's some good information on the temperature effects. Definitely something I didn't think about. I ended up having the deeper parts of the Mediterranean (based on a topo-map of the sea floor I found online) still having water, with Atlantis in one such small sea/lake (not sure about the distinction between them, honestly). You can see (roughly) what I ended up with here (https://drive.google.com/file/d/0B_5QIUB0exfpR3pWSWk5ZmtpSmc/view?usp=sharing)†. Unfortunately, I couldn't see on the topo what the depth was where I was drawing lines, I was going off of the color changes to figure out relative depth.

Still, while I figured the area surrounding Atlantis would be inhospitable, I didn't realize it would be that deadly from the heat alone. Nice to know!

As for why the humans don't leave the city... I expect the geography and distances to "safe" ground to be the main deterrents‡. Throw in the low overall population and I think it's quite believable that it's just not common for people to leave that way, and unheard of people to return that way.

So thanks, given me more stuff to think about. Atlantis is a hot sweaty muggy city.
________
†I was reducing the Meditteranean to a hex grid to both obfuscate the original terrain (my players aren't going to know they're on Earth to start with) and to simplify my job, so it's pretty rough, but you can sort of see Italy there in the middle. The pale off-white would be the salt flats, with darker blue being the deeper water. The greens and browns are the original coastline.
‡Based on my rough map, it'd be about 60 miles of sea and then 60 miles of salt flats before an escapee could reach Italy. And as Balayno established, that's going to be a fun journey.

[Balyano]

Just checked and I used the wrong numbers. I should have used the dry adiabatic lapse rate if the air is not saturated with moisture. Which is 10C/KM.

The average depth of the mediterranean is 1,500 M. So half the basin would be 15 C or 27 F or less hotter than sea level. Desert, but livable.
The deepest part of the mediterranean is 5,267 M. So if completely empty the bottom would be 52.67 C or 94.806 F hotter.
Since it's not completely empty it wont be that extreme.
I used to play with an interactive map online that let you raise and lower the sea level and see the results. But I can't find it and the only ones i can find only let you raise it above todays level.

So based on this map I'll guess that the seas that remain are at the 3000 M or lower mark.

http://publishing.cdlib.org/ucpressebooks/data/13030/6r/kt167nb66r/figures/kt167nb66r_fig005.gif

At 3000 M the land would be 30 C or 54 F above average.

Proximity to a large body of water matters alot. It evens out the temperatures.
Syracuse and Mosul are nearly the same latitude, but one is maritine and the other continental.
Syracuse
Average Low-High: January 45.1-58.6 F
Average Low-High: August 70.2-88.2 F
Record Low-High: January 37.4-65.5 F
Record Low-High: August 64.2-96.4 F

Mosul iraq has
Average Low-High: January 36-54.3 F
Average Low-High: August 75.6-108.7 F
Record Low-High: January .3-70 F
Record Low-High: August 58.1-120.7 F

Based on this (and kind of shaky) being 3000 M below sea level
salt sea
Average Low-High: January 99.1-112.6 F
Average Low-High: August 124.2-142.2 F
Record Low-High: January 91.4-119.5 F
Record Low-High: August 118.2-150.4 F

salt flats
Average Low-High: January 90-108.3 F
Average Low-High: August 129.6-162.7 F
Record Low-High: January 54.3-124 F
Record Low-High: August 112.1-174.7 F

[EscherEnigma]

That's... quite warm.

That tells me two things.

One, I shouldn't sweat the physics too much. Atlantis is a very warm place, but I have no interest in busting out the heat stroke rules. If it has designated "planting" and "harvest" seasons, that'll be based more on rainfall then temperature. Then again, I already established that it doesn't take many decanters to keep this place running, so maybe they don't rely on rainfall at all.
Two, the characters are going to be freezing when they leave the city and won't understand how people can survive such frigid environments as Thebes in August. They'll quickly trade out their loose linens for heavy furs.

[Balyano]

That's... quite warm.

That tells me two things.

One, I shouldn't sweat the physics too much. Atlantis is a very warm place, but I have no interest in busting out the heat stroke rules. If it has designated "planting" and "harvest" seasons, that'll be based more on rainfall then temperature. Then again, I already established that it doesn't take many decanters to keep this place running, so maybe they don't rely on rainfall at all.
Two, the characters are going to be freezing when they leave the city and won't understand how people can survive such frigid environments as Thebes in August. They'll quickly trade out their loose linens for heavy furs.

That's the temperatures at low elevations. I would assume that atlantis its self is on a highland region. What would be an island or a seamount after flooding. So there would be a inhospitable salt flat surrounding a hilly region. Climb up those hills and you are on a plateau that is warm, but livable. I don't know how much rain it would get, but during the messinian salinity crisis (the last time the mediterranian dried out) the highland regions got rain and the wild life surivived just fine. So what would become sicily, corisica, crete, ect. had elephants and hippos, and some of the smaller islands ended up with giant rabbits.