Which is the biggest Vault in Fallout 3
Which is the biggest Vault in Fallout 3
I don't know about biggest, but Vault 106 is definitely the toughest to navigate. Some people say it's just because every hallway looks the same, but I've heard that the exits actually changes locations. In this sense, it seems HUGE because it's easy to get lost.
Other than that, I think they're relatively small.