The Holy Monastery of Karakallou stands on a hillside between the Monasteries of the Megiste Lavra and Iveron. Of the traditions concerned with its foundation, the most likely is that which makes its founder a monk of the name of Karakalas of the early 11th century. The fact that the Monastery is mentioned in a deed of the Protos Nicephorus (1018) and omitted from the Second Typikon is some indication of its troubled history.
In the 13th century, after raids of pirates and Latins, Karakallou was totally deserted. It was brought back to life by the action of the Palaeologue Emperors Andronicus II and John V and of the Patriarch of Constantinople Athanasius. The number of monks increased and the Monastery was restored. Nevertheless, it again became the victim of pirate raids. In the 16th century, with the assistance of the Prince of Wallachia John-Peter - who in the end became a monk of the Monastery - and the subsequent permission of Sultan Suleyman, the Monastery was rebuilt. In the 17th century the Monastery of St Nicholas in Ismailia was donated to Karakallou.
During the second building phase at the Monastery, older constructions were restored and additions were made, but the reconstruction of a large part of the buildings became necessary after a major fire in 1875. Karakallou took an active part in the struggles to throw off the Turkish yoke. Of its buildings, a particularly noteworth piece of work is the tower of Peter, which was built in the 16th century and is the largest of the towers on the Holy Mountain.
Karakallou occupies eleventh place among the monasteries of Athos, and has five chapels, two outlying chapels, and 18 kellia. Its katholikon is a building of the 16th century with additions in later centuries. It is dedicated to Sts Peter and Paul. The present refectory of the Monastery is a building of 1875, but its original form was much older. Included among the treasures of the Monastery are vestments and liturgical vessels, the skull of the Apostle Bartholomew and of St Christopher, and a fragment of the True Cross. The library contains 279 manuscripts and some 2,500 printed books. Today the Monastery has around 30 monks.