Underground is the 20th chapter of Duke Nukem Forever. It has two parts.
Synopsis
Duke tries to shutdown the Hoover Dam from the inside.
Walkthrough
Part 1
Part 2
Easter eggs
- When Duke climbs out of the water, entering a small room where you can see the giant monster wreak havoc, somebody can be heard screaming "My anus is bleeding!" which is a reference to a cartoon short by Don Hertzfeldt.