Wikipedia
Necromanteion
The Nekromanteion was an ancient Greek temple of necromancy devoted to Hades and Persephone. According to tradition, it was located on the banks of the Acheron river in Epirus, near the ancient city of Ephyra. This site was believed by devotees to be the door to Hades, the realm of the dead. The site is at the meeting point of the Acheron, Pyriphlegethon and Cocytus rivers, believed to flow through and water the kingdom of Hades. The meaning of the names of the rivers has been interpreted to be "joyless", "burning coals" and "lament."
A site in Mesopotamos, Epirus was proposed as the site of the Necromanteion in 1958, but this identification is now questioned.