In Greek mythology, the Underworld was the land of the Dead. It was ruled by Hades and his queen, Persephone. It is said to lie beneath the earth, accessible by the sea.

Its two main divisions are Tartarus and Erebus. However, not much distinction is given between the two. Generally, Tartarus is the lower of the two, and Erebus is the section where the recent dead pass through. The Underworld is said to be a mystical, shadowy place where ghosts constantly roam around as if in limbo. The ghosts' plight is often compared to a "miserable dream".

The Underworld's geography is detailed in Dante's Inferno. The path down to it leads to where the river Acheron pours into Cocytus, the river of lamentation. Charon is the ferryman who rows passengers across the water to a farther bank, where they encounter a gate to Tartarus. Cerberus, a monstrous three-headed dog, guards the gates and permits souls to only come in once and never leave. The dead is judged and placed either in everlasting torment if they were bad, or to the Elysian Fields, a land of eternal bliss.