Vault-Tec Headquarters

The Vault-Tec Headquarters building is located in the Vernon Square area of the Washington, DC ruins.

Building History
This was Vault-Tec's base of operations around the DC area. From this location (specifically, from the Vault-Tec Mainframe), you can learn the locations of Vaults 87, 92, 106, and 108.

Enemies
Resistance inside the building consists of security robots and turrets; the models inside are regular Protectrons, Sentry Bots, Robobrains, Mister Gutsies, and one special model of the Robobrain - the Masterbrain - on the same floor as the Mainframe. You can turn off the Masterbrain and all other security robots in the Vault-Tec Headquarters if you use the correct command on three employee terminals in the Mainframe area. Alternatively, you can destroy Masterbrain and use it to shut off all other security robots.

Super Mutants have been encountered fighting the robots in the Guest Relations area. It seems they have been using the Vault-Tec Headquarters as a massing point, as Gore Bags, which are a common find within Super Mutant bases, are located in the Guest Relations men's restrooms.

Guest Relations

 * A Tales of a Junktown Jerky Vendor book on a table up the broken stairs on the right side of the room, in the cafeteria area. It is meant to only be accessible when you go down from Administrations again. However, with some tricky jumping it can also be reached if you jump from the highest point of the broken staircase.

Corporate Offices

 * One Nuka-Cola Quantum is located in the most Northwestern room on the second floor. It is on the bottom shelf of a bookcase. There's a door covering a hole in the floor in this room.
 * A Big Book of Science in the room directly east of, and connected to, the room containing the Nuka-Cola Quantum on the second floor. The room with the book should have almost no floor. When you stand in the doorway and look straight through at the opposite wall, you will see two bookshelves slightly off to the right on the eastern wall. The Big Book of Science is on the top one. It's very difficult to see, and the easiest way to obtain it is to shoot it down.
 * Stealth Boy; northwest corner, top floor, in a storage closet just above the room with a random loot safe that also sometimes contains a Stealth Boy. (You have to walk around the edge of the missing floor to get to the closet.)
 * A Pre-War Book on top of a garbage can next to aforementioned safe.

Administration

 * An issue of Grognak the Barbarian on a curved desk in a private office. The room is at the very west of the area.
 * 7 Vault-Tec lunch boxes are located in a closet in the most northeast room.

Related Quests

 * Agatha's Song: The Vault locations retrieved here helps with the optional portion of the quest.

Appearances
The Vault-Tec Headquarters only appears in Fallout 3.

Bugs

 * Once you've destroyed the Masterbrain, you can shut down all the other robots, then you return to the Guest Relations area through the door on the right side that was inaccessible before, now go back to the Offices through the door on the left and you might find all the robots you previously destroyed, alive and functioning (Sentry Bots keeps moving) though they won't walk, attack and neither show on the compass as enemies or friends.
 * It is possible for the PC to get stuck in a hallway barricade. On the second floor, southeast area, there's a pile consisting of a desk, filing cabinet, and shelving. Jumping onto the desk could get you wedged in, as there's a section of ceiling protruding downward that prevents your exit. Crouching may allow exit.
 * It is possible to become stuck in the ladies washroom in the Vault-Tec Administration. Every time the player, or a follower, tries to leave, he/she will become stuck and teleport back.
 * It is entirely possible that once you've destroyed the Masterbrain by fighting it, and attempt to shut down all other robots, that all other robots and turrets will remain active and continue fighting you. Confirmed on Xbox 360, the old version of the game.

YouTube Videos
Locating Vault-Tec Headquarters lzpGSXalvNE