The Los Angeles Vault

Bethesda Softworks / Via fallout.gamepedia.com

The Los Angeles Vault was the very first vault, and played heavily into the plot of the original Fallout game. It was created by Vault-Tec Industries, and served as a prototype for all their other vaults. It opened 15 years after the Great War that decimated Los Angeles, and its dwellers formed the city of Adytum near its entrance.

Many flocked to the city and the vault below it, including a grotesque monster called the Master, a product of a process called "forced evolution" that transformed him into a hybrid of a vault computer and a man. The Master turned the vault into his lair, and conducted experiments on its dwellers in an attempt to create more creatures like himself. Instead, he ended up creating a race of brutes known as the super mutants, who served as his personal army.

The vault was destroyed during the events of the original Fallout when a nuclear device was set off under the structure by the game's protagonist.