Presidential Metro

The  is a network of metro tunnels that is added to Fallout 3 in the Broken Steel add-on.

It connects the Presidential Sub Level beneath the White House with Adams Air Force Base and The Capitol Building's East Wing. Protected and maintained by a computer system called M.A.R.Go.T., the area is guarded by Sentry Bots and swarming with ghouls.

Unmarked quest: Fatal Attraction
A holo-tape titled "Sorry, My Darling" is located up a flight of stairs on a bench near the exit to the capital building east wing. Finding and listening to it will start the unmarked quest Fatal Attraction.

Notable loot

 * A Scoped .44 Magnum in a partially collapse room to the left off the northeast tunnel.
 * A Power Fist on a skeleton in the irradiated southern end of the eastern tunnels.
 * A number of Sensor Modules and Cameras.
 * A Mini Nuke in one of the abandoned metro cars; you must look at the end of the train, where there is a skeleton inside with a Laser Pistol...going inside may get you trapped, so save before entering this car (you should be able to reach the nuke without entering the car)
 * Various different types of ammo.
 * Nuka-Cola Quantum in the Equipment Room, which connects the western and eastern lines.

Trivia

 * This secret metro system was likely constructed to quickly evacuate the President and his staff to the more secure location of Adams Air Force Base in the event of nuclear war. From the appearance of the White House terminal, however, the Line has not been in use at least since the Great War, and may never have fulfilled its original purpose.
 * If you have a high enough Science skill or you found the Senator's ID, M.A.R.Go.T. will tell you that the last time the Metro line was in use was 200 years and 3 months before the current date.  So whether or not the President made it to AAFB, someone certainly seems to have taken advantage of this escape route.

Appearances
The appears in the Fallout 3 add-on Broken Steel.