Fallout 3 locations project
Super Mutant Bunker
The Super Mutant Bunker is a base of operations for the Super Mutants located in the middle of their two trenches under The Mall. The Super Mutants occupy all the territory east of the Washington Monument. It appears as if the Brotherhood of Steel once occupied the bunker, be it for a brief period, before it was retaken.
There are two entrances to the Super Mutant Bunker. The eastern entrance is at the bottom of a pit protected by a trap. The western entrance is in the western trench behind a sandbag wall. Both entrances are also booby trapped. Once you enter you may be able to see a Super Mutant Brute.
Also note that if the Super Mutants outside are sufficiently damaged they may retreat, then occasionally they may run into the bunker. You can draw them outside if you dislike enclosed fights.