Fallout 3 (Walkthrough) with DLC's -> Underworld
The residence of the ostracized sentient zombies (unlike their wild counterparts) of the Federal District. Located within the National History Museum. Since the latter hosted an exhibit on the mythology of hell and the afterlife during the Great War, most of the Underground's inhabitants base their views on the exhibits there. Most "smoothskins" who visit the Underground are tolerated as long as they don't cause trouble.
Members of the Brotherhood of Steel are unwelcome, apparently due to their habit of shooting zombies on sight. If the hero chooses to detonate Megaton, Moira Brown will survive and reappear in the Underground, mutated into a zombie. It's a small settlement with a bar, a hotel, a hospital, and "stylist" J. One of the robots in the Underground is named Cerberus. This is a reference to Greek mythology, where the hundred-headed dog guarded the approaches to Hades. The bodyguard's name, "Charon," also relates to this theme, as it was the name of a ferryman who, for a fee, transported the souls of the dead across the Styx.
Charon is a character who can join the hero on their travels. The dungeon is where the quests "Sign Charon Up for Your Party," "Finish Him with a Headshot," and "Riley's Rangers" are obtained. Important NPCs: Winthrop, a mechanic, will exchange 5 scrap metal for a stimpack, Rad X, or Rad Away; Tulip, a merchant, will give the coordinates of Paradise Lost if spoken to;
Mr. Crowley, who resides at Carol's Place, will give the hero the quest "Finish Him with a Headshot" to obtain 4 keys. Upon completion, he will head to Fort Constantine and, if the hero has already obtained the armor, will begin tracking them, as will Dr. Burrows, who, if asked, will revive Riley.
Source: stopgame.ru, GameGeezer56
See also:
Fallout 3: The Mall and its environs