Vaults are a core part of Fallout’s lore. These nuclear shelters were designed by Vault-Tec before the nuclear war. Unbeknownst to most of the public, Vault-Tec had an obsession with experiments that would make Aperture Science blush. To that end, the majority of the shelters were created to conduct scientific experiments on their inhabitants. Here’s our list of the ten most horrifying vaults from the Fallout universe.

10. Vault 101 (Fallout 3)

Vault 101 stands out from the others as the only one that wasn’t intended to open again. Instead, the Overseer would be given complete control over a facility that would remain closed indefinitely.