Tartarus
Tartarus within (Nessus) is the largest and most secure prison in existence.
Tartarus is as far beneath Hell as heaven is high above the earth. A place so far from the sun it is hemmed in by three layers of night, which surround a elysian bronze wall which in turn encompasses Tartarus. It is a dank and wretched pit engulfed in murky gloom.
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, 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 sinners.
Tartarus has a number of inhabitants. When Cronus, the ruling Titan, came to power he imprisoned the Cyclopes in Tartarus. Zeus released them to aid in his conflict with the Titans. The gods of Olympus eventually defeated the Titans. Many, but not all of the Titans, were cast into Tartarus. Prisoners are guarded by Hecatonchires. When Zeus overcame the monster Typhon, the offspring of Tartarus and Gaia, he threw it, too, into the same pit.
Originally, it was used only to confined dangers to the gods of Olympus. Tartarus has later become became the place where the punishment fits the crime. For example Sisyphus, who was both a thief and murderer, was condemned for eternity to push a boulder up a hill only to have it roll down at the top. Also found there was Ixion, the first human to spill the blood of a relative. He caused his father in-law to fall into a pit of burning coals to avoid paying the bride-price.
The fitting punishment was to spend eternity on a flaming wheel. Tantalus, who enjoyed the confidence of the gods by conversing and dining with them, shared the food and the secrets of the gods with his friends. The fitting punishment was to be immersed up to his neck in cool water, which disappeared whenever he attempted to quench his thirst, and lucious grapes above him that leapt up when he tried to take a hold.
Rhadamanthus, Aeacus and Minos are the judges of the dead and choose who goes to Tartarus.