Sunken Sewer

The Sunken Sewer is a rather small, heavily radiated (due to many waste barrels) underground location, containing some feral ghouls and probably a glowing one. It can be reached from the northern part of Dupont Circle.

Notable Loot
A U.S. Army: 30 Handy Flamethrower Recipes book can be found on an average safe. On some shelves there's also enough (3 doses) RadAway to survive getting into this location without specific precautions (provided you can fight the ghouls fast enough).

Note
Sunken Sewer may be a reference to Sunken Sewers below the Imperial City in Elder Scrolls IV: Oblivion.