The Pitt Underground

The Pitt Underground is an area in the Fallout 3 DLC The Pitt and contains The Pitt's Power Plant. It can be accessed in The Pitt's Steelyard, near a wrecked train entering an inaccessable metro tunnel. The second exit leads to Haven's courtyard in Uptown.

Both entrances are initially locked or closed. The manhole in the Steelyard can be opened with the Power Plant Key whereas the doors in the floor between the Underground and Uptown can only be opened if you assist Werhner in Free Labor. If you do not assist him, there is no way to open these doors.

Enemies
There are about a dozen Trogs in the area, coming in groups of 3 to 4, with the occasional individual popping up out of nowhere (possible spawning). There is one instance of a massive group (4-5) spawning in pursuit of you as you reach the bottom of a ramp. Close to the Steelyard entrance, two trogs can be seen canibalizing some unfortunate person from behind some bars.