As far as I can tell, no one's started an idea list thread for dungeons.
Here's the criteria: full maps and room-by-room outlines aren't necessary. Please include the general structure or system housing the dungeon, a brief description of the history, theme, and/or layout, and finally why adventurers would be interested in exploring it.
1. Claydum's Lair
This dungeon is housed within a floating island. The island is shaped like an upside down cone. On the top of the cone, housed within inward sloping walls, lives a tribe of trolls, a tropical ecosystem kept in check by Claydum - a red dragon who lives inside the island.
The entrance to this dungeon is located at the bottom of the cone, up through a waterfall. The dungeon requires adventurers to traverse upward, either by climbing sheer rock walls, or using magic, to get from one room/cavern to the next, moving toward the treasure horde, and Claydum, in the top loft. Along the way, adventurers will face oozes, trolls, and other obsticles planted by Claydum.
Bump?