Reasons for a dungeon?

[UndeadArcanist]

I've noticed that most dungeons are either the former underground dwelling of a notable individual/race that has been abandoned and overtaken by [insert monstrous race here], or the secret construction of a mad spellcaster of some sort. I would love to hear your ideas for a new setup for a dungeon.

I'll start with my idea. Basically, there used to be a fortified and prosperous city near the base of a volcano. One day, the volcano erupted and spread ash over the entire area, burying the city (yes, like Pompeii.) In the present day, the players are recruited by an archaeologist who needs help exploring an underground complex which turns out to be the buried city. The players must travel through the sewers from building to building to fight the construct and undead guards that still remain at their posts.

[kraftcheese]

This has been done before but the concept is still slightly different to what you listed: an underground maze (constructed by someone completely sane) used to contain a being/artifact/place of power deep below the surface of the world. It's populated by constructs, summoned beings and mortal creatures honorbound to stop anyone from reaching the being/artifact/place.

It would allow for some diplomacy with the intelligent creatures considering you might want to destroy the thing in the centre (or some lying about how you want to destroy it if you really want to free/use it).

[Mastikator]

A dungeon can serve as a storage locale for valuable goods/treasures.
It can house prisoners very securely and it can be used to house VIPs in a very defensible location.
It could also be a mine that was later retrofitted/reinforced into a dungeon.
Or a tunnel from one spot to another that was later expanded upon.

It make perfect sense that you might find interesting stuff in dungeons under a buried city, since there wouldn't have been time to evacuate all of the valuables. You can also have had some monster flee into the dungeon when it was being buried and then get trapped there, the right kind of monster might survive the eons buried.

[ClintACK]

A Proving Ground -- by getting through it, the PCs prove their worthiness to some group or other.

A God Did It -- a version of "a wizard did it" in a polytheistic world where at least one of the gods is completely inscrutable. It might be a clever plot to attract, test, train, and equip the heroes the world will desperately need. Or perhaps the god is just completely insane. Who can tell the difference?

Entertainment -- anywhere from a Gladiatorial display to a Reality TV show. There are people watching the PCs battle their way through clever scenarios purely for entertainment purposes.

[Misereor]

I remember doing a full redesign of the dungeon from Keep on the Borderlands, because I quite frankly found the design ridiculous.

Rainwater and underground river create limestone cave system.
Minerals in water feed various fungi. Small creatures feed on fungi. Larger creatures feed on smaller creatures. Even larger and nastier creatures feed on those, etcetera.
At some point in history intelligent creatures (in this case Elves) discover the caves and expand them to create a secret burial crypt with themed traps.
Much later, people digging a well in the keep stumble across the caves and use them as a secret entrance/exit.
Even later again, adventurers stumble across old keep and eventually discover hidden entrance.


In the same campaign, a clan of Dwarves had a city that was dug into the perfectly smooth sides of a canyon dug through a mountain range by the creator gods.
Said "gods" were actually the ancestors of all the humanoid races in the world, whose high tech mining vessel had crashed on this backwater planet many millennia before. The canyon was created by a laser cutter intended for large scale mineral extraction. The mineral in question was something akin to "spice" from the Dune setting, which when absorbed by organisms would cause mutation and grant mental abilites. Depending on the mind of the individual in question, it could manifest as arcane, divine, or natural magic abilities. Since the atmospehere was permeated by the stuff, you had standard D&D races, but in concentrated doses it could grant godlike abilities (if you survived taking it). At both poles were orbital elevators, defunct, but with control rooms, access corridors, and a few security systems still functioning. Ancient desert pyramids also had various purposes. The end dungeon of the campaign was an abandoned starship in orbit, infested with the tyrannid like monster race that had destroyed the star spanning civilization.

Anyway the point was, that it made for surprises for the players, when what they assumed that they were in standard dungeon designs which suddenly exhibited very different mechanics than they expected. (None of them had played Might and Magic 4 & 5, so it took quite a while before they caught on.)

[Arkhios]

Far from unique I reckon but I had my campaign take place in a very old city where the new layers of the city have been built above the old city, over and over and over again, over the course of centuries, the levels below eventually having become sort of abandoned dungeons, although people still live in the more habitable zones in rather questionable conditions. Better off upper class living on the top levels, naturally, while the waste gradually flows underneath them. Plot hook is that there is something important and likewise dangerous buried within, and that the players are likely to venture deep down there at some point.

[Jay R]

It was built by the denizens of the underworld, as a way for them to reach the surface, but also as an outpost to protect them from the surface dwellers.

[viking vince]

In a fantasy world where many dangers can come from overhead (like Dragons), a ruler may decide that the most defensible royal dwelling might be underground.

[Joe the Rat]

Thus far, I have used three (overlapping) categories:
1) Vaults and Catacombs - a place to keep things safe, kept secret, or where you keep your (maybe) dead.
2) Basement Ruins - only a few layers deep, these are the basements and sub-basements of ancient structures - keeps and castles and temples and the like. Sometimes bits of the ruin are visible above ground, sometimes they're grown over, sometimes someone has gone and built a city on top of them.
3) Dwarves did it. Dwarves generally prefer to build into rock, not on top of it. Anything of Dwarven (or other Stone race) make tends to be mostly underground.

Converted mines and buried structures (I've got deserts and swamps) are on my list of things to use, but they have not come up in game yet.

[DigoDragon]

In a fantasy world where many dangers can come from overhead (like Dragons), a ruler may decide that the most defensible royal dwelling might be underground.

Like the Kaers in Earthdawn, huge labyrinthine cities built deep underground to hide its residents from the Horrors.

[cobaltstarfire]

One of the "dungeons" I was in had a section that the GM was going to fluff as the midbosses menagerie if we went into it, we ended up skipping it but I thought it was a neat way to make sense of the random monsters that often appear in premades.

[Kami2awa]

Somewhere in the world, there must be spells, items or monsters that create underground spaces (and prevent them collapsing) much more easily than can be done in real life. Umber hulks might be a possibility. Once you have those, underground construction becomes very appealing due to its security and defensibility.

[Madbox]

One of my favorite video games, Final Fantasy Crystal Chronicles, had quite a few interesting dungeons that I plan on ripping off some day.

Many of the dungeons were basically wilderness exploration, that was justified by the expedition's purpose. The planet was covered in poisonous fog, and the only way to ward it off required materials that had to be harvested from rare trees.

Some highlights were:
1. Veu Lu Sluice, a waterworks powered by magical plants. Since the plants do the work, no one goes there and it is overrun with monsters.

2. River Belle Path, an old trail that was abandoned when the new highway was constructed. There's only the faintest remnants of human habitation, a few crumbled walls and busted up bridges. It is now overrun with monsters.

3. Mochet Mannor, the mansion of an intelligent monster. Obviously, filled with monsters.

4. Tida, the ghost town. Their caravan failed to collect what they needed, and everyone died. Now overrun with monsters.

[AslanCross]

Red Hand of Doom's original final dungeon was simly a temple of Tiamat; for my campaign I redesigned it to be a part of a worldwide planar prison seal for Tiamat. It had sufficient room for living quarters, a place of worship, a barracks, and other dungeon elements.

I still forgot to put a toilet into it, though.

[Jay R]

I still forgot to put a toilet into it, though.

Your monsters must get really bad-tempered.

[ClintACK]

I still forgot to put a toilet into it, though.

That's what the pit trap is for. Added bonus: now the spikes get a disease or poison effect.

Alternately, get a couple of Otyughs.

[Cealocanth]

A few I've used in the past:

Underground bandit encampment, hanging out in an old ruin to raid the countryside
A tomb of a particularly wealthy king, trapped and occupied by monsters to ward off grave robbers.
A Fallout-stye Vault that has been broken into. The monsters are taking advantage of the life support facilities.
The den of a burrowing monster race. Kobolds, deep dwarves, troglodytes, etc.
An extensive cave-system currently occupied by an evil cult.
An old barrow with burial treasures within, now occupied by the walking corpses of the restless dead whose final rest you have disturbed.
An old abandoned castle crawling with undead. Dungeons don't have to be underground.
A buried monument left behind by the Ancients, designed to contain a secret evil within, with trials so difficult as to ensure that only a technologically and morally advanced civilization could access its power.

[kraftcheese]

Your monsters must get really bad-tempered.
And very smelly.

Maybe one of the traps should just be opening the door to the poo room...

[Joe the Rat]

And very smelly.

Maybe one of the traps should just be opening the door to the poo room...So using that one...