Infinity Net Collection vol.1
Three levels. The first is a straightforward sewage-filled arena, with a few areas out of the action, for loading up on weapons and ammo. The second is split into two pieces... a warzone (lots of baddies, bobs, and S'pht'kr) and a small lava-filled arena. The third... well, "You are in a maze of twisty passages, all alike."
Levels in map "Infinity Net Collection #1":
La Terre De La Mort
Gettysburg
The Mir Space Station