Hiding a City

[Almec Sandkeer]

In my homegrown world I have a city which serves as the gateway to a region heavily populated by wizards, sorcerers, clerics, etc and those non-casters who support their work. Just on the other side of this city lie hordes of those pithy, common folk unendowed with magic. Commoners, kings, nobles, orc bands, etc. I'm looking for a way to ensure the city is either hidden or very nearly inaccessible to anyone without magic, but would be relatively easy even for a low-level caster or someone who grabbed a Wand of Something to approach.

The idea is that this first line of magical defense prevents the city from being readily assaulted by roving bands of folk, but a young magic user or an approaching caravan with knowledge of the city's defenses can attain admittance beyond the magical barrier where the city guards will decide to open the gates or not.

So far I've considered something as simple as having the approaching character cast some sort of low-level spell that is shared across both arcane and divine lists. For example, there is a specific pile of rocks, or clump of trees, and a person would cast Light on one of those to be admitted beyond the barrier to approach the city. But I don't know what sorts of spells could make up the barrier. If there are ones which could make a city-scale invisibility possible that would be ideal, but at minimum I want it to prevent entry or at least make it very difficult without the proper access mechanism.

I'm not against a certain portion of the city's defenses being "Because I'm the DM and that is how it works" but if a good way exists in the published material to do this I would like to avoid DM fiat where possible. I prefer not to use things which are inaccessible to players without necessity.

[BowStreetRunner]

You could use some sort of Epic Spell (http://www.d20srd.org/indexes/epicSpells.htm) to accomplish this. Place the city in a mountainous region with an epic spell that include the Compel seed targeting non-casters. Anyone who enters the mountains has their sense of direction confused - they are compelled to follow the mountain trails around the central valley where the city resides, but without realizing they are doing so. A non-casting scout might report back that he searched every trail in the mountains and found no signs of a valley, while a lowly wizard apprentice might wander up and find the path to the valley easily.

[Crake]

You could use some sort of Epic Spell (http://www.d20srd.org/indexes/epicSpells.htm) to accomplish this. Place the city in a mountainous region with an epic spell that include the Compel seed targeting non-casters. Anyone who enters the mountains has their sense of direction confused - they are compelled to follow the mountain trails around the central valley where the city resides, but without realizing they are doing so. A non-casting scout might report back that he searched every trail in the mountains and found no signs of a valley, while a lowly wizard apprentice might wander up and find the path to the valley easily.

An additional option would be to use an epic spell to make a permanent, huge Mirage Arcana making the city essentially invisible as well

[Almec Sandkeer]

I haven't worked much with Epic spells, but here's my crack at an epic spell to turn aside the curious. A similar spell, based on the Conceal or seed could be used to make the city invisible. I have it set on a small isthmus from which it magically transports people into the realm beyond it. I figure it's feasible for a level 21 wizard with around 30 Int to have developed and cast this back in the mists of time, when the city and region were first founded.


Seed: Compel
Spellcraft DC: 51
Components: V, M
Casting Time: 100 days
Range: 75 feet
Target: 512 10-ft cubes
Duration: Permanent
Saving Throw: Will negates DC 30
Resistance: Yes

Factors: Change from target to area four 10-ft cubes (+10), Increase area by 100% 7 times (+28), Permanent duration (x5), Increase casting time by 100 days (-200), Additional participants - 2 9th level spell slots (-34)

Anyone who enters the area of effect from the side designated by the caster is compelled to turn aside and skirt the around the area, being convinced that their knowledge of the area is sufficient. Those with a particular interest in the region such as scouts are convinced their curiosity is sated, those with no particular interest disregard the existence of the region entirely. Magical light of any kind negates the spell's effect in its area, revealing the area of negation as a lightly shimmering curtain. A Will saving throw negates the effect as well.

[zlefin]

here's a way that requires only moderate dm fiat:
The entry is a special teleportation circle; to activate the circle you have to push a specific button on the wall, there's tens of thousands of buttons on the wall; and a resetting trap randomly changes which button is the activation button every minute or so.
The correct button will be identifiable by having a special magic aura that anyone can find by using the spell detect magic.
Using the spell "magic aura" for the resetting trap might work, or something else might be better.

[laeZ1]

This sounds like yet another problem solved by... Energy Transformation Field! (http://dndtools.eu/spells/magic-of-faerun--20/energy-transformation-field--1756/)
Using ol reliable ETF, a young spellcaster can pump 5 1st level spells into the special area, and it will activate the teleport spell imbedded in the ETF. Though I think the epic spell idea is better. I'm just promoting my favorite spell.

[Piggy Knowles]

I suggested this for someone years ago, and liked the idea enough that I incorporated it into the campaign world I'd designed. It could easily be adapted here as well.

THE FRAGMENTED CITY

The hidden city exists - but it is in pieces. Scattered throughout the world there are small villages. The villages seem odd. They pop up out of nowhere, and though they are tiny (frequently under a hundred people), there is a surprising amount of wealth found in the villages, and the building structure is more like something you'd see in a city than in a small village.

Essentially, to hide their city, epic spellcasters broke it into many tiny pieces, and scattered it around the world. Each "piece" seems like a self-sustained village from the outside. However, to the spellcasters of the city itself, when walking down the street, they can appear in the connected street as if the great city was whole, even if that connected street is on the other side of the world.

So, draw out the map of your city, and break it apart like pieces of a puzzle. If you're a true member (or can fake it), then when walking down the street, you can function as though the city were whole, instantly appearing at where the street should connect. An illusion of you remains in the old city until you return. If you're an outsider, though, you can walk up and down that road and nothing will seem strange.

You can make it fairly simple to detect if you'd like - a faint magical aura can clue you into the illusory doubles that remain, and you can make it something like a particular invisible Arcane Mark that allows access. So, by finding one of the spellcasters who can travel through this way, using See Invisibility on them to locate their secret mark, and then Arcane Mark to duplicate it on the party, you can unlock the city.

[The Random NPC]

I don't know if this will help, but I heard an idea someone had about putting portable holes in portable holes to get a much larger space than normal. Using enough hole, and bottles of air, you could build an entire city in, for example, the basement of a bar.

[Skysaber]

Transport is easy. D&D has tons of ways to do it, including ETF, or just having a teleport trap whose trigger is "someone casts a cantrip on this stone."

Hiding the city, on the other hand, is more difficult. You could try putting it into an inaccessible place, mountain, sea floor, sky, etc. The trouble is, this is D&D, and no place is inaccessible enough for it to remain hidden for any length of time.

The spell Distance Distortion was once ideal for things like this. You could make roads that go completely around a wide circle to avoid you look and feel and travel just like they went a short, straight path right through. You could also stretch farmer's fields so they appeared to fill in the space that you took up. So on an imperial census map, your hidden city wouldn't exist, just straight roads and plowed fields as far as the eye could see.

Doesn't stop people from seeing your magical city. But once you made it invisible via other means you could prevent a bean counter going over maps from saying "Hey, you know district X and X? Why don't we have farmland in this huge empty blot?"

In previous editions it was even fun to play around with Hallucinatory Terrain, as to anyone who failed their save, the illusionary land was completely real. So you could take a crater, and paste an illusion of land over the top to make it look like a mesa, and people could live up there, even build towns and whatnot. The only problem is that every so often someone would make their save and mysteriously plummet to their deaths through the ground.

What you probably want to do is make for your city a custom item, like a Weirdstone, but instead of preventing scrying and teleportation within its six mile radius effect, have it instead plant a Suggestion to subconsciously avoid the place, that whatever they're looking for, it isn't there. Then provide anyone with spellcasting ability automatic immunity.