Ten kilometres north of Kalavryta, this is believed to be one of the oldest monasteries in Greece (though the current building dates from the 20th century). Its prized relic is a wax icon of the Virgin Mary, said to have been made by St Luke and supposedly discovered in the nearby cavern by St Theodore and St Simeon in AD 362 (though it most likely dates to around AD 1000). It's popular with pilgrims; a strict dress code applies.
The original monastery was destroyed several times over the centuries, most recently in 1943 when the German army executed all the monks and burned it down. Inside, head up the stairs to the atmospheric church, where frescoes have survived the destruction cycles; the famed icon sits on the far right of the iconostasis. Beyond the church is the grotto where the icon was found (and a dragon defeated by its power).
Many people, especially those on the train, hike the pretty, if steep, 3km walk from Zahlorou, the village stop on the Diakofto–Kalavryta railway. It's also easily accessed on the Diakofto–Kalavryta road. A taxi from Kalavryta costs around €30 (including a 30-minute wait time).