Another shout for Adense Epic Dungeon. It really is unique and truly unique dungeon crawl, where nothing is as you'd expect.
Parts of the dungeon appear to be made by interlocking lots of large rocks and architecture pieces together rather than using the normal dungeon tile sets. The result is sections of uneven floored irregular passage, with holes in the floor, pools of water, and often the route on hidden in a chaos of boulders.
I'm a ex potholer (spelunker if you're American) and this is one of the very very few gaming enviroments I've ever experienced that actually feels familiar. (admittedly there'a less flesh eating skeletons in Gaping Gyll and Kingsdale Master
Cave