Two levels. One is a conversion of Bob World HQ (no credit to Mark Conahan, the original creator), using the alien textureset, and the other is a small insanely busy arena with a raised cross in the center.
An arena level with a large pool in the center. Half of the bottom rises and falls slowly, making a good high spot (or missile block). Teleporters speed up end-to-end travel, and light switches control who's visible and who isn't...