The Sicherheitsunterkunft

The Sicherheitsunterkunft is a sealed underground city, similar to the Arcology. While Rin is being pursued through the swamp by a pack of mutant weeds, she accidentally triggers the city's entrance mechanism, and later learns enough about the autonomous control system to allow Shasta entrance as well.

When the pair discover nothing but skeletons dressed in black and red uniforms, they believe the city may be abandoned. However, they later learn that there are still plenty of eligible men.