Vault 91 is near the Glowing Sea, but heavily guarded by the Gunner mercenaries. It doesn't give you much good loot, so don't even bother getting involved. I don't remember where Vault 81 is, although I think it's kinda west of the Railroad HQ, but it's still active, isolated to keep the citizens safe, and it's overall a really nice place to hang out. Vault 111. Enough said. There's another Vault I found, I just can't remember where.