Monongah Overlook shitter!
This mysterious button is curious indeed. This is the end point from a shaft that shoots you up from deep within the earth and up through a crapper after you fuck around with a nuclear launch. Convenient and gross as all hell. Imagine if someone was in there when you arrived?
Some irony in the second picture. Vault Boy disapproves of reducing the gravity of nuclear war to a dance of bluffing and one-upmanship!