Monastery of Mega Spilaio (translated as "big cave") is located 10 km from the town of Kalavrita and is the oldest monastery in Greece. It was built on a steep slope 120 meter high rocky hill in the year 362 A. D. by two brothers monks Simeon and Theodore.

According to legend, the brothers had the same dream in which they were told to go to Achaia and find the icon of the mother of God. The way they had to indicate local cowgirl. And so it happened. They met a shepherdess Afrosinia, and she showed them the path to the cave where they found the icon. The monks expanded the cave, built a chapel and remained to preach in these places. The cells of the monastery were built around the entrance to the cave where the icon was found.

It is believed that the icon was created by the Apostle Luke, wax almost 2000 years ago. This icon is also called "Preporucena" as the mother of God holding the infant on her right arm. The miraculous icon of the Mother of God and still kept in the monastery and is considered its most important relic. Interestingly, many of the fires, which were subjected to the monastery throughout its history, has been unable to destroy this Shrine.

In 840, the monastery was burned and restored only in 1285 Andronikos Paleologos. Since then, the monastery became one of the richest in the country. Mega Spilaio survived two fires in the 1400s and the 1600s, then the fire destroyed the Church and a library with rare manuscripts. In 1934, another fire destroyed the priceless Holy relics. In 1936, the monastery was restored, but in December 1943 suffered serious destruction at the hands of the German occupiers. Then were shot 22 monks and other members of the monastery, and their bodies thrown into the abyss.

Mega Spilaio is a historical relic of Greece. Thousands of pilgrims come here every year to touch the miraculous icon of the Mother of God and worship the Holy relics, surviving a fire. The monastery is in a beautiful scenic location and very attractive for tourists.