I searched for quite a while here and looked around. There are some fantastic dungeons and a few cave areas that are interesting.
The thought comes to mind of mapping a region of the Under(insert favorite name here) Not room details, but regional details. For example the entire realm of Moria would be interesting to see a best guess as to what it looks like.
The reason I bring it up. My own campaign (not RPG) has an UnderWorld to it. I've been thinking it would make more sense to actually have something of a multi level / 3D mind set to it. If there are Mountains above ground then there are likely to be caverns in a good percent of them. Even large bodies of water, chasms, and other such random thoughts at the moment.
Thanks for your time.