Cocytus

Cocytus or Kokytos, meaning "the river of wailing" (from the Greek Κωκυτός, "lamentation"), is a river in the underworld in Greek mythology. Cocytus flows into the river Acheron, across which is the underworld, the mythological abode of the dead. There are five rivers encircling Hades. The River Styx is perhaps the most famous; the other rivers are Phlegethon, Lethe, and Acheron.