Tartarus

In classic mythology, below Uranus (sky), Gaia (earth), and Pontus (sea) is Tartarus, or Tartaros (Greek: Τάρταρος, from τάρταρον "tartar encrusting the sides of casks"). It is a deep, gloomy place, a pit, or an abyss used as a dungeon of torment and suffering that resides beneath the underworld. In the Gorgias, Plato (c. 400 BC) wrote that souls were judged after death and those who received punishment were sent to Tartarus.