Located in downtown Las Vegas, Nevada, Vault 21 was a unique Vault experiment: everyone in the vault was equal, it was created with a perfectly symmetrical layout, and the dwellers settled their differences via games of chance. Reliance on luck to solve problems created what might be considered the perfect realization of anarchy: a society in which everyone is equal and no one has an advantage over the others. Vault-Tec ensured that every person admitted to the vault when it first sealed was a compulsive gambler, and were unable to decline when Vault-Tec personnel running the vault informed them that this was how the vault was to be run. The original dwellers then passed on their lifestyle to their children and so on.
However, as with all utopias, the peace was not lasting. Sometime between 2271 and 2281, Robert House planned an occupation of Vault 21. Resisting attempts to be assimilated into his empire, the inhabitants agreed on gambling to settle the issue. The game they played to settle the deal was blackjack and almost the entire vault was in attendance. In a risky bet, the supporters of House won against the opposition, and Vault 21's interior was stripped of its useful electronics and equipment and partially filled in with concrete, forcing the dwellers to resettle in the wasteland and on the Strip. At Sarah Weintraub's and Michael Angelo's (a.k.a. Sheldon Weintraub) insistence, House left the topmost level intact and allowed the Weintraubs to establish a hotel there, which became another source of income for his fledgling empire.
Vault 21 is one of the extremely rare experimental vaults which successfully protected its inhabitants while fulfilling the parameters of its experiment. The experiments in most other Vault-Tec vaults ended up killing or permanently altering their inhabitants. Although Vault 3 was a control vault, intended to recolonize the surface after an extended period of time, when its door was opened the Fiends slaughtered its residents and took over.
The vault's main cog door has been transformed into a sign advertising the vault/casino. "Vault 21" is emblazoned on it in neon lights. The vault entrance is an above ground building which contains the Vault 21 gift shop. It is run by one of the only two native residents to have remained, Sarah. Stairs lead from the gift shop down into the vault.
The vault has been converted into a casino and hotel. There is a central atrium with gambling tables, a hallway with living quarters, including Sarah's room and a guest room that the player can rent. Another door leads to the cafeteria/diner. The lower levels were filled with concrete by Mr. House and are inaccessible except for the maintenance level, which is accessible from the basement of The Tops, where the Chairmen appear to have tried to break in. This level consists of a long hallway with a few small rooms branching off of it. The elevator in Benny's suite leading to it is locked unless he is attacked in the Tops Presidential suite, and the tunnel ends in another locked door.
The Tops houses an elevator that goes down to the basement and connects via a blown open wall to the service areas of Vault 21. This elevator is normally locked and unable to be picked, but is automatically unlocked if Benny is given the chance to flee when confronting him at The Tops.
There is a locked door at the end of a hallway in the vault that can be unlocked using console commands. An invisible part of the Vault will appear if you walk a little forward. There are no lights and this part ends-up with two staircases leading to nowhere.
Although the theme of this vault revolves around gambling, and there are gaming tables around, it is not possible to gamble in this location.
No doors in this vault feature a gold stripe and the number 21, but instead are all marked "No Access". The same is true for Vault 3.
The lights in the vault appear very dirty and rusted, and are actually the models seen in ruined vaults, such as Vault 34.
The eastern billiards room contains a jukebox named "Jukey The Jukebox". Other than the name, it doesn't appear to be special in any way.
If you leave items in the locker of your room and later get the reputation of "Wild Child" for The Strip, then you cannot rent the room or retrieve the items.
Players may make this their personal vault/home once they are given a room by Sarah.
Vault 21 is the only known vault that does not still possess its cog-shaped blast door. Instead, the door was converted in to a sign advertising the hotel.
Oddly enough the current entrance to Vault 21 leads all the way to the gift shop without any apparent modifications. This would mean that, unless the current access stairs were added for the vault's hotel conversion, the gear door and entrance chamber were entirely above ground.
If you look to the right when you walk in, you will see the Vault 101's bulletin on the wall with only a couple changes made to it, such as the Vault 101 bake off ad being changed to Vault 21.
There is a working light switch in the player's hotel room.
The sub-basement hallway tunnel appears incomplete when seen in the GECK, there's also a door that supposedly leads to the hallway, but it's blocked by a large chunk piece.
There is a slightly undersized terminal in the gift shop.
Vault 21 is a reference to the card game "Blackjack", where 21 is the highest sum and its limit, usually declaring an instant victory. This supports its gambling theme.
Vault 21's lower levels being filled with concrete is a subtle reference to the Silver Slipper Casino, as it was rumored that the casino was filled with concrete by Howard Hughes, the man who was the basis for Mr. House.
The computer in Sarah Weintraub's room contains an email from a Charlene Tann who mentions her husband Biff Tann. This is likely a nod to the Back to the Future trilogy; the films' antagonist is named Biff Tannen.
pcps3xbox360 If you take the tour with Sarah Weintraub, your companions may disappear and not reappear when you exit the vault.[verified]
pcxbox360ps3 Sarah may not recognize Vault 21 jumpsuits as vault gear, but will trade for them normally at the usual price.[verified]
xbox360 Sometimes when you take the tour with Sarah Weintraub, she will walk with you out of the gift shop and then stay still above the stairs leading to the hotel part of Vault 21 and will be unable to talk to.[verified]
xbox360 Vault 21 has a high probability of causing the game to freeze during loading screens. [verified]