Tartarus

In classic Greek mythology, below Heaven, Earth, and Pontus is Tartarus, or Tartaros (Greek Τάρταρος, deep place). It is either a deep, gloomy place, a pit or abyss used as a dungeon of torment and suffering that resides within Hades or the entire underworld with Hades being the hellish component. In the Gorgias, Plato (c. 400 BC) wrote that souls were judged after death and those who received punishment were sent to Tartarus. As a place of punishment, it can be considered a hell. The classic Hades, on the other hand, is more similar to Old Testament sheol.