Acheron River, Greece

In ancient Greek mythology, Acheron was known as the river of woe, and was one of the five rivers of the Greek underworld. In the Homeric poems the Acheron was described as a river of Hades, into which Cocytus and Phlegethon both flowed.

The Roman poet Virgil called it the principal river of Tartarus, from which the Styx and Cocytus both sprang. The newly dead would be ferried across the Acheron by Charon in order to enter the Underworld. The Suda describes the river as "a place of healing, not a place of punishment, cleansing and purging the sins of humans."

More info: http://en.wikipedia.org/wiki/Acheron