This is a strong fortress crowning the peak of the Pityos hill in NE Leros, at a height of about 600 metres above sea level. There are no visible traces of ancient occupation of the site. A chrysobull of 1087 associates the castle with the Blessed Christodoulos, founder of the Monastery of St. John the Theologian on the neighbouring island of Patmos. It appears that at the time it was in a poor state; the grant included the walls, a church with some monastic cells and some other buildings in ruinous condition. Four coats of arms in various parts of the monument testify to the Hospitaller efforts to strengthen the defences. On the west side of the fortress stands the church of the Virgin, probably dating from the 18th century, with icons of considerable religious significance. At the centre of the fortress standos another church called Fangoklissia (=church of the Franks). In the first half of the 20th century the castle was used by the Italians as a barracks and observation point, and concrete was used for various modifications.

The Ecclesiastical Museum is managed by the Orthodox See of Lerosand contains relics and icons from all over the island.