A mixture of a found map and a bit of my own design, this map has 3 levels.
I am working around this as a concept map for a Necromancers hideout, a mini-BBEG for my party.

My application of this is for a crater lake that has the meteor still in it. It has "poisoned" the underground spring with necrotic energies. The site was built around it, with the locals believing the place to have been blessed by a god of the dead without realizing its full potential.