This ancient complex is small but comes with a gripping backstory. According to Homer and Herodotus, it was a place to consult with an oracle (nekromanteio) who channelled dead ancestors for advice. Pilgrims took an elaborate ritual meal, then processed through a labyrinth into a hall where ghosts appeared. A 1998 study posited a duller hypothesis (fortified farmhouse, yawn), but the site is still evocative, with massive walls of hewn boulders and access to the cool, shadowy underground hall.
Per ancient sources, the site was in use from at least the 8th century BC, and the extant walls and labyrinth date from the late 4th century BC. The Romans burned the place in 167 BC. Sometime after the 15th century, a small monastery was built over the old temple ruins. In the 19th century, a koulia (an actual fortified farmhouse) was built; it was fully restored in 2015. The site ticket includes admission to the acropolis of Ephyra, a short walk to the north. Established in the Late Bronze Age (14th century BC), the site is now only rubble, with a few stretches of wall that are rougher, more ancient versions of the ones at the nekromanteio. If it's not too hot, it's worth a stroll just for the view over the lush river valley.
The site is about 20km south of Parga, on the hill on the east side of Mesopotamos. In high season, you must park a few hundred metres away and walk up to the gate and ticket office. Alternatively, book a guided excursion through International Travel Services in Parga, or take a taxi, starting at €30 one way. This way (or in your own car), you can combine it with a boat excursion up the Acheron (the river the dead were said to cross) in nearby Ammoudia, on the coast.