Vault 74

Vault 74 is one of the Vault-Tec vaults. The vault was not mentioned in any game and appears only in the game files of Fallout: New Vegas.

It was originally made by Bethesda Softworks developers for the official Fallout 3 G.E.C.K. tutorials. Despite not actually appearing in the game file of Fallout 3, it strangely appears as cut content in the game files of Fallout: New Vegas, although is only accessible through the use of the console commands.

Background
Many fiends live in this vault.

Layout
Vault 74 is small, consisting of just an atrium, a clinic, an overseer's office and no living quarters.

Related quests
The vault comes with a simple quest called Exploring Vault 74. The quest can be started by simply entering the vault (by the use of console commands) and taking the Vault 74a overseer's log:

Appearances
Vault 74 appears only in the game files of Fallout: New Vegas. Due to its original nature of being a test demonstration, it is most likely to be considered non-canon.