The underworld is the place in Greek mythology where people go when they die. The underworld is controlled by Hades, one of the three main gods. The underworld's gates are guarded by the three-headed dog, Cerberus. The underworld was surrounded by five rivers. The Acheron was the river of woe, the Cocytus was the river of lamentation, the Phlegethon the river of fire, the Styx, the river of the unbreakable oath by which the gods took their vows, and the Lethe the river of forgetfulness. When entering the underworld, Charon would take those with gold coins to the underworld. Not everyone could enter, because not everyone had golden coins to pay the fare. 