Vault 27

Vault 27 is one of the Vault-Tec Vaults. As part of the Vault Experiment, this Vault would be overcrowded deliberately. 2000 people would be assigned to enter, double the total sustainable amount. The location of this Vault is unknown. It can be assumed that the Vault failed due to the possibility that it could not provide enough food or water for the large population, and contagious diseases may have also been rampant throughout this Vault due to overcrowding.

Appearances in games
This Vault does not appear in any game and is mentioned only in Fallout Bible.

It also should be noted that a group of a hundred or so ended up both dying and the survivors of that group formed the Vipers.