|Dungeon of the Crystal Eye|
|Name||Dungeon of the Crystal Eye|
|Location||Land of Ooo|
|Notable inhabitants|| Demon Cat,|
The Dungeon makes its first appearance in the episode of the same name. It is a perilous stronghold with many monsters, puzzles, and chambers that serve to guard the Crystal Eye. Due to its dangerous contents, Princess Bubblegum requested that it be sealed off. She planned to do this by having Finn and Jake set up a bunch of signs warning people not to go inside. It is populated by frightening creatures like Bugbears, a Demon Cat, a skeleton that looks similar to or is the skeleton from the episode "Wizard," a demonic creature that poses as one's "guardian angel," a mimic treasure chest that vomits golden treasure, a Bucket Knight, and Demon Eyes.
- Certain elements of the Dungeon look similar to the Lich's lair, as shown briefly in "His Hero."
- This and Joshua's dungeon are unlike regular dungeons; a dungeon usually refers to a type of underground prison, but instead they are underground places where a certain thing or item is hidden, guarded by trials. This is reminiscent of the dungeons found in video games.