The monastery is situated 10km away from the town of Kalavrita.
Built on the wild and steep side of a 120m high rocky hill there is a unique view from the monastery's balcony. The monastery's cells have been built around the entrance of a cave.
The monastery was founded at this location in 362 A.D. by two brothers, Symeon and Theodore, because an icon of the Virgin Mary was found deep inside the cave where there's also stream. The icon was discovered by a shepherd girl and was created by Apostle Luke from mastic and wax.
In 840 A.C. the Mega Spileo was burnt down by the Iconomachs. In 1285 Andronikos Paleologos rebuilt it and from then on, this monastery became one of the richest in the country.
In 1400 and in 1600 the monastery went through another two fires at which point the church was burnt down along with the precious library containing rare manuscripts.
In 1934, the monastery went through again with another fire during which invaluable relics were destroyed.
The monastery was rebuilt, in 1936, but suffered severe destruction in December 1943 from Germans. Germans executed 22 monks and all other staff members and their bodies thrown over a cliff.
In the hall of the monastery relics kept great and unique treasures.