The nekromanteion of Acheron was built on a hilltop specially flattened for this purpose. A rectangular enclosure in polygonal masonry, entered from the north, surrounds a square building, the main temple, which two parallel walls divide into a central hall and two side aisles. Underneath the central hall is a rock-hewn subterranean room, the dark palace of Persephone and Hades, whose ceiling was supported by fifteen poros arches. Archaeological evidence dates the temple to the early Hellenistic period (late fourth-third century BC). A group of rooms and warehouses surrounding a central court was added to the original building in the late third century BC, during a second building phase. The new annex was used for lodging priests and visitors.
Architecturaly the building resembles a mausoleum, or grandiose funerary monument, like those built for various monarchs in Asia Minor and the East in the late fifth century BC (e.g. the monument of Mausolus at Alikarnassus). Made of excellent polygonal masonry, it had iron-clad gates and was divided internally into corridors, adapted to the chthonic cults and their rituals. During these rituals, the followers entered a dark hallway and were led by the priest to the appropriate preparation chambers, where they fasted and underwent catharsis, before performing a sacrifice. They then entered a large dark hall, where they met the souls of the dead.
Hundreds of vases containing offerings, lamps, and smaller vases, often decorated in the Athenian West Slope style, were discovered during excavations. Millstones, sea-shells, farming and construction tools, and figurines of Persephone and Cerberus were stored in the warehouses.