Said to be a secret forge owned by the Hephaestus Cabin during the civil war, it was rediscovered by Leo Valdez. It can only be opened by demigods with the blessing of Hephaestus, and has lately become a home for the son of Perses so that he cannot destroy anything important. The bunker is well-guarded and everything is locked down so tight that destruction of the items inside is impossible without them being unlocked.