A Vault-Tec nuclear shelter, Vault 12 was located under the town of Bakersfield, California, and designed to house a thousand people. As intended by Vault-Tec, the blast doors did not close entirely after the bombs fell, resulting in the ghoul town of Necropolis.
Under the sprawling metropolis of Bakersfield, lies the technological magnificence of Vault 12. Built with every amenity in mind for the prospective Vault Dweller, Vault 12 was given the "Pressed Vault Suit" award for attention to preparedness. Buried far underground, the protection that Vault Dwellers will receive will be unprecedented. Much like all other Vaults, Vault 12 has been fitted with the newest in Vault Water Purification Systems. Able to take even the waste located in the sewers of Bakersfield, this system is able to deliver over 15,000 gallons of pure, refreshing drinking water every day.
Vault 12 is essentially identical in layout to the other vaults encountered by the player. The first level contains the Medical Lab and entrance, the second is entirely living quarters, and the third houses the recreation area, armory, and command center. The command center notably lacks the space for an Overseer which appears in other vaults - this is potentially because the vault was never intended to be inhabited for a long period. Indeed, as the vault has never entirely sealed, it is very dirty and weathered through 85 years of exposure and lack of maintenance. Only a handful of doors, computers and the elevators remain operable.
A number of glowing ones still inhabit the vault. They can be evaded fairly easily by sneaking past, though they will attack the player if the water chip is removed but the water pump has not been repaired. This is one of the few occasions when glowing ones demonstrate to the player that they retain their full mental faculties.
The water chip is located in the command center. It is easily spotted as it is attached to the only operational computer.
If the first glowing one that one would encounter is left alive, and the water chip taken with out repairing the water pump, he will remain even after the other ghouls have died of dehydration, and comment on this fact.