Underworld

Underworld was an exhibit in The Museum of History, now a home to many ostracized non-feral ghouls of Washington, D.C. It is located inside the Museum of History, and exists as a small city, complete with a bar, inn, clinic, clothing store, and even a self-proclaimed "hair stylist."

Most humans are tolerated, as long as they don't cause trouble. The Brotherhood of Steel are not welcome because of their hostility towards ghouls and the Brotherhood's tendency to shoot them on sight.

Background
The museum was featuring an exhibit on the concepts of Hell and the afterlife during the time before the Great War, as most of the remaining exhibits (including the name of that section of the Museum as well) are all themed as such. Doctor Barrows is the mayor of Underworld. Because of the small nature of the town, his civic duties take a backseat.

Exterior
Outside of the Museum of American History, the player will be greeted by a ghoul named Willow, a self-proclaimed 'envoy to the wastes'. A Brotherhood of Steel outpost is located nearby, and several super mutants are present across the road at The Mall.

Griffon will set up his aqua cura scam outside if Take it Back! has been completed, but only in the Broken Steel add-on. The player can reach the town by going through the double doors under the giant skull once inside the Museum of History.

Interior
When you first enter, you'll be standing in front of the main hallway. Underworld Outfitters, a store run by Tulip, is in a room on the left side of the hallway, while Winthrop's office is opposite and a little farther from the entrance. The doors in the back lead to The Chop Shop, where Doctor Barrows works.

Heading up either set of stairs will take you to the overlook. The Ninth Circle is a bar run by a shady ghoul named Ahzrukhal and is on the left side from the main entrance. Carol's Place, where you can rent a room or grab a bite to eat, is located on the right from the main entrance. In the large room at the end of the overlook, Moira Brown will be selling miscellaneous items and asking you to continue with research for her survival guide (if you destroyed Megaton). Snowflake, the resident barber, will be hounding you for a haircut.

Inhabitants

 * ¹ Unconscious as long as Reilly's Ranger quest isn't completed.
 * ² If she survives Stealing Independence and is spoken to after completion.
 * ³ If you destroy Megaton without killing her.
 * † Can be found wandering around in front of the entrance to the Underworld in the room with the Woolly Mammoth. He must be freed from his prison cell during the Finding the Garden of Eden quest.

Appearances
Underworld only appears in Fallout 3.

Behind the scenes

 * The large ruined painting on the second floor of the Concourse is "Dante and Virgil in Hell" by William-Adolphe Bouguereau.
 * Also relating to Dante and Virgil, the bar "Ninth Circle" is phrased after the travels of Dante and Virgil through the nine circles of hell. The Ninth Circle is the final circle, where traitors including Lucifer himself.
 * Many of the inhabitants' names are related to the hell concept, including: Cerberus (Hades' 3-headed dog), Charon (the ferryman of the River Styx), and obviously nurse Graves.