Hades (mythology)

   The people of ancient Greece thought that the earth was flat. Down below it, they believed, there was a great, gloomy region to which people went when they died. This underworld the Greeks called Hades after the name of the god who ruled it. Pluto was another name for this god of the underworld.
   In Hades there was supposed to be a wide river—the Styx. The spirits of the dead had to cross the River Styx to enter Hades. On the bank of the river an old boatman, Charon, was always waiting to row them across. A huge dog with many heads stood guard at the gate of Hades to keep anyone who entered the underworld from escaping. The name of this dog was Cerberus.