|Location||South-East Washington inside the Museum of American History|
|Main Locals|| Winthrop|
|Places of Interest|| Carol's Place|
The Ninth Circle
|Related Quests||* You Gotta Shoot 'Em in the Head|
Underworld is a town located in the Capital Wasteland in Fallout 3. It can be found inside the Museum of American History. The city is home to mostly Ghouls, who treat the city as a refuge from the outside world, where they are constantly attacked by Super Mutants, Raiders and Brotherhood of Steel soldiers.
The town is kept in good shape by the maintenance engineer Winthrop, he will ask you to collect Scrap Metal due to the lack of resources in town. Underworld is guarded by a Mister Gutsy robot called Cerberus, he hates Ghouls with a passion but he's been programmed to protect them.
If the Lone Wanderer blows up Megaton in Power of the Atom, Moira Brown will survive the blast and be transformed into a Ghoul. She will become a resident of Underworld which allows you to continue with The Wasteland Survival Guide.
 You Gotta Shoot 'Em in the Head
- Main Article: You Gotta Shoot 'Em in the Head
 Reilly's Rangers Quest
- Main Article: Reilly's Rangers Quest
 The Amazing Aqua Cura
- Main Article: The Amazing Aqua Cura
This Broken Steel quest can be started by asking Griffon for a bottle Aqua Cura. The water is irradiated but Griffon will deny the claim. The Lone Wanderer will need to find evidence to prove him wrong.
 Hired Help
- Main Article: Hired Help
 This Old House
- Main Article: This Old House
In this unmarked and repeatable quest Winthrop will give one Rad-Away, Rad-X or Stimpak for every 5 pieces of Scrap Metal given to him. It might be a better idea to use Scrap Metal in Walter's Scrap Metal instead.