Adolf Hirémy-Hirschl, Souls at the Acheron, 1898.
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.
According to later traditions, Acheron had been a son of Helios and either Gaia or Demeter, who had been turned into the Underworld river bearing his name after he refreshed the Titans with drink during their contest with Zeus. By this myth, Acheron is also the father of Ascalaphus by either Orphne or Gorgyra.
In Dante’s Inferno, the Acheron river forms the border of Hell. Following Greek mythology, Charon ferries souls across this river to Hell. Those who were neutral in life sit on the banks.