What you can find inside a dungeon?

[LadyN]

Depends. How deep is it? Is it inside a building or underground?

[Inspector_Spinda]

Chained up naked girls

[IdiotWithPencil]

Slaves, lots, and lots of tortured slaves....=0 and a key

[NickRowler]

Skeletons of explorers who have failed
Booby traps
Shackles and jail cells

[Kelheor]

a colony of moths
a small ferns and moss corner

[DukeOfOool]

Infinite stairwells and uneuclidian geometry (e.g. you have to walk 5 times around a 90° corner, before arriving at the same crossection, instead of the normal 4 times) because I like confusing everybody and build my dungeon whithout common sense, but with a knack for cosmic horrors. And because I'm already here, also mimics, mimic coins, mimic furniture, mimic corpses; make everybody paranoid. And also enemies hiding indefinitely akward behind corners only waiting for that single unlucky person to walk past them.

[skicoak]

Domanatrixes, swingers, people with unusual sexual kinks, sheep, a variety of huge ....

Oh! You mean the other kind of dungeon!

Then implausible wall torches/light fixtures.

[KizKat]

A gauntlet of death traps, beasts that hide in the darkess and natural dangers (poisonous mushrooms, slippery moss, poison gas), all guarding the one thing worth braving the horrors for. Riches beyond your wildest dreams (put there by a dragon who is still guarding it, roll initiative)!

[DualDragons]

Corrosive cubic jellies.

Maybe floating magical jellyfish? I'd put them in my dungeon if I had one.

[darthmongoose]

Some of my favourite things...

Hallucinogenic fungi,
Pressure plates that set off ancient, rusty deathtraps or cause the room to start slowly filling with sand or water,
Secret doors,
Things that look like doors or treasure but are actually shapeshifting monsters!
Goblins, kobolds, slimes, dragons, animated skeletons!
Room full of weird, terrified looking highly lifelike statues you suddenly realise are people petrified by a cockatrice or basilisk,
Demon or devil who has been trapped in a magic circle for years and offers you anything you want if you just free them,
Chasms with an invisible bridge.
Comfortable little home area that houses a surprisingly polite and civil lich who invites you to stay...

[DualDragons]

Comfortable little home area that houses a surprisingly polite and civil lich who invites you to stay...

Reminds me of this fellow from Konosuba xd

[CommanderMarty]

You find the abyss that will stare back if you look into it.

[Snickerdoodles]

Historically, storerooms.

Dungeon

Few Norman keeps in English castles originally contained prisons, though they were more common in Scotland. Imprisonment was not a usual punishment in the Middle Ages, so most prisoners were awaiting trial, sentence or a political solution. Noble prisoners were not generally held in dungeons, but lived in some comfort in castle apartments. The Tower of London is famous for housing political prisoners, and Pontefract Castle at various times held Thomas of Lancaster (1322), Richard II (1400), Earl Rivers (1483), Scrope, Archbishop of York (1405), James I of Scotland (1405–1424) and Charles, Duke of Orléans (1417–1430). Purpose-built prison chambers in castles became more common after the 12th century, when they were built into gatehouses or mural towers. Some castles had larger provision for prisoners, such as the prison tower at Caernarfon Castle.[4]

Although many real dungeons are simply a single plain room with a heavy door or with access only from a hatchway or trapdoor in the floor of the room above, the use of dungeons for torture, along with their association to common human fears of being trapped underground, have made dungeons a powerful metaphor in a variety of contexts. Dungeons, as a whole, have become associated with underground complexes of cells and torture chambers. As a result, the number of true dungeons in castles is often exaggerated to interest tourists. Many chambers described as dungeons or oubliettes were in fact storerooms, water-cisterns or even latrines.[5]

[PapaDom]

An Endboss. I had to learn it the hard way.
There was once this Library type of dungeon where I had the quest to find a specific book.
After finding the book, I wanted to exit the dungeon but was stopped by the boss before leaving.
It looked like an old lady who said some gibberish like, "Don't leave with the book without a notice."
And I don't know what she meant, so I started battling with her. Her skill set was quite impressive, but the overall stats of her were nothing to concern. I defeated her in like five turns.

[magnavarra]

you can find another dungeon. Or China. Or if you enetred a dungeon in China welcome to Canada I guess? Sorry bad geography here

[Pizza_Agent]

Normal keys and boos key

[gmaximin]

Electronic tablets and visual displays explaining the architecture and history of the building. Eventually some gruesome illustrations here and there, just so that visitors don't feel cheated on their entrance ticket's price.

[Blizzriel]

A chest containing a piece of bread, meat, or vegetable that is in pristine condition despite being kept in a musty dungeon for thousands of years.
An ecosystem that relies on energy from the corpses of adventurers who died in the dungeon since there's no access to sunlight.
The remnants of a long-dead civilization that was experimented on/corrupted by some otherworldly force.
Fire. Lots of fire. Though for some reason, you never have problems because of smoke inhalation...
A well that can magically transport you to another well in a different part of the dungeon.
Bob, a guy who decided it was easier to take over a couple of rooms in a monster-infested dungeon than pay rent on an apartment. Actually has a pretty sweet place.
A mirror. If you're not careful, your reflection will try to pull you into it and take your place.
A hatch that leads into another dungeon below the first.

[thel3tterm]

Something valuable, and a multitude of things which are trying to maim, kill or misdirect you in an attempt to keep you from that valuable thing.

[drcharlotterodricks]

Mutant dragons and lewd cat girls