Dungeon Design

[Panton]

My suggestion would to be change your idea of what a dungeon has to be. For instance, why does it have to underground?
You could magically suspend it in the air, or put it deep underwater, or in a pocket dimension that abides by different laws of nature.

Or you could change the change the rules.
Why does it have to be a trudge through a bunch of rooms until the big baddie? Maybe it's a moving dungeon that keeps teleporting your heroes outside of it, and part of the challenge is they have to find it again, somewhere else.
Or maybe all the monsters are clones of the adventuring party at every level, a room full of level 1s, then 2s, 3s, etc.
Or it could be the same room over and over again, but each time add a new threat.

For more inspiration about crazy, interesting and unique takes on dungeons I suggest you take a look at the Goblins webcomic.
(here's a link to a spot where they enter a dungeon, but I also suggest you read it from the beginning if you're interested) ---> http://www.goblinscomic.org/02012011/

[Knightvision]

I've got to check out the Dwarven Fortress, it sounds cool.