|The following is based on Van Buren and has not been confirmed by canon sources.|
This cave winds its way into the side of a mountain. Its passages are dark, damp, and foreboding. The main passage branches into several side passages that end in rooms. Some of these rooms are used as lairs for various monsters while others are simply dead ends.
The mystery caves can only be discovered in one of two ways. First, the player can track the creatures that have been invading the fields of the Twin Mothers tribe. Second, the player can be given directions here by either a guard in the fields or by the male chieftain of the tribe.
Immediately upon entering the cave the main passage branches to the right and opens into a larger rock strewn cavern. The secondary passage leads to a small room scattered with litter and debris. The large cavern is the lair of several giant slugs. A second cavern to the left of the lair appears to have collapsed.
At the rear of the slug lair is an exit that leads further into the mountain. Soon this passage branches into three rooms. The first is a room scattered with debris and the remains of dead animals, the second is the lair of a colony of giant albino ants, and the third is the queen ant's chamber. The ants will attack anyone entering their domain.
This area was intended to be nothing more than a combat area. Providing an opportunity to kill for "fun, sport, and experience".
The Twin Mothers Mystery Caves did not appear in any of the published games. It was to appear only in Van Buren, the canceled Fallout 3 by Black Isle Studios. It is not certain if it will appear in any future Fallout game