In the Fallout series, Vaul-Tec's Vaults were originally marketed to the public as a safety measure in the event of a nuclear conflict. However, as many players know, each vault was also the subject of its own unique social experiment in an attempt to breed the strongest survivors in the future. Vault 75 is no different, however, it is a difficult one to find. Unlike Vault 111 and 114, which players visit during Fallout 4's main questline, Vault 75 is a little more obscure, and will take some searching for in order to find it.