User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-115.127.15.85-20121201045529

Tartarus is a gigantic place, surrounded by the flaming river  Phlegethon  and triple walls to prevent sinners from escaping from it. It is guarded by a  hydra  with fifty black gaping jaws, which sits at a screeching gate protected by columns of solid  adamantine, a substance akin to diamond - so hard that nothing will cut through it. Inside, there is a castle with wide walls, and a tall iron turret. Tisiphone, one of the  Erinyes  who represents revenge, stands guard sleepless at the top of this turret lashing a whip. There is a pit inside which is said to extend down into the earth twice as far as the distance from the lands of the living to Olympus. At the bottom of this pit lie the  Titans, the twin sons of  Aloeus , and many other sinners. Still more sinners are contained inside Tartarus, with punishments similar to those of Greek myth.(from Wikipedia)