Vault 74

Vault 74 is one of the Vault-Tec vaults located in the Capital Wasteland. Not much is known about its fate except that it was overrun by raiders. It is small, consisting of just an atrium, a clinic, and an overseer's office.

Related quests
The Vault comes with a simple quest called "Exploring Vault 74". You start the quest by simply entering the vault and you complete the quest by taking the Vault 74 Overseer's log:

Appearances
Vault 74 is a Vault that the Bethesda Softworks developers made for the official G.E.C.K. tutorials and it does not appear nor is mentioned anywhere else. Given that, the location is likely non-canon.