Vault-Tec Headquarters

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

This was Vault-Tec's base of operations around the DC area (it is unknown if this was their main headquarters). From this location (specifically, from the Vault-Tec Mainframe), you can learn where Vaults 87, 92, 106, 108 and 112 are.

Over the front desk right when you enter the building, suspended from the ceiling is Vault 101's door.

The only resistance inside the building are the leftover security robots and a few turrets. The models inside are: Protectron, Sentry Bot and Mister Gutsy. Also, there is one special model of the Robobrain on the level where the Mainframe is. It is called the Masterbrain and is hostile towards you. You can turn it off (and every other security bot in the facility) if you access three terminals that are placed around that area.