Inside the walls of Tartarus sits a wide-walled castle with a tall, iron turret. Tisiphone, one of the Erinyes who represents vengeance, stands sleepless guard at the top of the turret lashing her whip. Roman mythology describes a pit inside extending down into the earth twice as far as the distance from the lands of the living to Olympus. The twin sons of the Titan Aloeus were said to be imprisoned at the bottom of this pit.