Info (English)
Ancient Greek mythology saw the "Acheron", sometimes known as the "river of woe", as one of the five rivers of the Greek underworld.
Most classical accounts, including Pausanias (10.28) and later Dante's Inferno (3.78), portray the Acheron as the entrance to the Underworld and depict Charon ferrying the souls of the dead across it.
The Homeric poems describe the Acheron as a river of Hades, into which Cocytus and Phlegethon both flowed.
The Roman poet Virgil called the Acheron the principal river of Tartarus, from which the Styx and the Cocytus both sprang. The newly dead would be ferried across the Acheron by Charon in order to enter the Underworld.
According to later traditions, Acheron had been a son of Helios and either Gaia or Demeter, who was turned into the Underworld river bearing his name after he refreshed the Titans with drink during their contest with Zeus.
The river called Acheron with the nearby ruins of the Necromanteion (oratory of the dead) is found near Parga on the mainland of Greece opposite Corfu. Another branch of Acheron was believed to surface at the Acherusian cape (now Karadeniz Ereğli in Turkey) and was seen by the Argonauts according to Apollonius of Rhodes. Greeks who settled in Italy identified the Acherusian lake into which Acheron flowed with Lake Avernus. Plato in his Phaedo identified Acheron as the second greatest river in the world, excelled only by Oceanus.
Following Greek mythology, Charon ferries souls across the Acheron to Hell. Those who were neutral in life sit on the banks
He claimed that Acheron flowed in the opposite direction from Oceanus beneath the earth under desert places. The word is also occasionally used as a synecdoche for Hades itself. Virgil mentions Acheron with the other infernal rivers in his description of the underworld in Book VI of the Aeneid. In Book VII, line 312[13] he gives to Juno the famous saying, flectere si nequeo superos, Acheronta movebo: 'If I cannot bend the will of Heaven, I shall move Hell.' The same words were used by Sigmund Freud as the dedicatory motto for his seminal book The Interpretation of Dreams, figuring Acheron as psychological underworld beneath the conscious mind.

Info (Greek)
Στην αρχαιότητα πίστευαν ότι ο Αχέρων αποτελεί τον ποταμό εκείνο, τον διάπλου του οποίου έκανε, σύμφωνα με την αρχαία ελληνική μυθολογία ο «ψυχοπομπός» Ερμής παραδίδοντας τις ψυχές των νεκρών στον Χάροντα για να καταλήξουν στο βασίλειο του Άδη. Η κάθε ψυχή, περνώντας από το πορθμείο του Χάροντα, έπρεπε να δώσει από έναν οβολό για τη μεταφορά, ενώ αξιοσημείωτη είναι η περίπτωση του Μένιππου, τον οποίο αναφέρει ο Λουκιανός, ως τον μοναδικό που διέσχισε τον Αχέροντα χωρίς να πληρώσει. Στο δρόμο του ο ποταμός Αχέρων διασταυρωνόταν με τους Πυριφλεγέθοντα και Κωκυτό, στο σημερινό χωριό Μεσοπόταμος, στο σημείο όπου βρίσκεται το αρχαίο Νεκρομαντείο του Αχέροντα. Η αρμοδιότητα του Νεκρομαντείου του Αχέροντα ήταν διαφορετική από αυτή των Δελφών και της Δωδώνης. Ο σκοπός του δεν ήταν η παροχή χρησμού αλλά η διευκόλυνση της επικοινωνίας των επισκεπτών με τις ψυχές των νεκρών συγγενών τους. Αχέρων, Κωκυτός και Πυριφλεγέθων συναποτελούσαν τους τρεις ποταμούς του Άδη.