The monastery’s katholikon is a one-room church with a spacious narthex to the west, located on the perimeter of the lake. It was probably founded in the 11th century and is historically linked to the recapture of Kastoria by the Byzantines after a brief period of Norman domination. The church is decorated with frescoes in the late 12th and early 13th century. After part of the church collapsed, the katholikon was repaired and the sanctuary and the southern outer wall were repainted in 1259. It is the only monument in Kastoria in which imperial portraits are depicted on the exterior frescoes next to one of the oldest depictions of the Root of Jesse. According to researchers, this is the depiction of Alexios I Komnenos, associated with the foundation of the monastery, and Michael IX Palaiologos, victor of the Battle of Pelagonia, associated with the renovation of the monastery. The monastery had a rich estate and a close connection with the settlement of Mavrochori on the opposite shore of the lake.
In the first half of the 16th century, a chapel dedicated to St. John the Theologian was added to the south side of the katholikon and decorated with frescoes in 1552, the work of the painter Efstathios Iakovos, prothonotary of Arta.