Acheron

Acheron, also called Mavropotamos (black river), is the river located in Epirus, in northwestern Greece. 

In ancient Greek mythology Acheron was known as the "River of Woe" and was one of the five rivers of the Greek underworld. Charon was the ferryman of Hades, the god of the underworld. He carried the souls of the newly deceased across the rivers Styx and Acheron. These rivers divided the world in two. That of the living and that of the dead. A coin was placed on the mouth of the dead person, as fare for Charon. Those who could not pay for it, or those whose bodies were left unburied, had to wander the shores for one hundred years. 

The Suda lexicon, from the 10th century, describes the river as a certain place in the middle of everything; in it occurs a receding and a flooding of waters, until reaching complete inundation; it is a dim and dark place. Yet, Acheron is like a place of healing, not a place of punishment, where cleansing and purging the sins of humans occurs.

In Sigmund’s Freud book The Interpretation of Dreams, Acheron is referred to, as the psychological underworld, the place beneath the conscious mind.