The Church of Panagia Mavriotissa, catholicon of the monastery of the same name, lies four kilometres to the southeast of Kastoria, by a stand of ancient plane trees on the shores of the lake. Tradition has it that the monastery was named after the lakeside village of Mavrovo.

The church was probably built in the 11^th century. It is a single nave timber roofed building ending in a semicircular stepped conch to the east. On the west side there is a spacious square narthex or lite . A chapel dedicated to St. John the Theologian was added to the south wall in the 16th century; it is decorated with wall paintings dating to 1552, attributed to Eustace Iacobou, priest and protonotarios (administrative official) of Arta.

Fragments of the frescoes decorating the church have survived in the sanctuary, on the west wall of the nave, the east and south walls of the narthex and the outer south wall.

In the sanctuary conch, two pairs of enthroned Evangelists and the Concelebrating Prelates are depicted below the enthroned Virgin with angels.  The pediment on the east wall has depictions of the Ascension above the Annunciation, healers, stylites and Saint Euplous. The crack running across the east wall reveals that the entire upper section must have collapsed and been restored, at which time the damaged scenes must have been added to, along with the figure of a monk at the feet of Our Lady. According to a barely legible inscription, it was he who saw to the renovations.

The iconographic program on the west wall has survived in its entirety, showing scenes from the Pentecost in the pediment, the Washing of the Feet, the Crucifixion and the Betrayal in the next zone, and the Assumption below. The door pilasters are adorned with depictions of two monk saints - Alexius, known as the Man of God, and Ioannis Kalyvitis.

The impressive depictions of the Second Coming on the east and south wall of the lite are from the same period. Flanking the entrance are depictions of Saints Constantine and Helen, and a later fresco of the Baptism. Of particular iconographic interest are the figures of the damned above the Five Saints of Sebaste. Subjects of particular iconographic interest include the Concelebrating Prelates in the sanctuary; the depiction of Fainting Virgin Mary and the grotesque figures of the servant and the soldier at the Crucifixion; the incident involving Jephonias in the representation of the Assumption of the Virgin Mary; and the types of punishment at the Second Coming. Despite earlier views which assigned the wall paintings to the 12^th century, the above scenes indicate that the decoration can be dated to the first decades of the 13^th century. The reconstruction and completion of the painted decoration in the upper part of the sanctuary, the Baptism in the narthex, and the external wall paintings date to the second half of the 13th century.

On the exterior south wall there are representations of the Root of Jesse, Agios Demetrios and Agios Georgios with two imperial figures. According to the accompanying inscriptions, the figures to the right are Emperor Michael VIII Palaeologus and another Comnenus dynasty emperor. He is probably Alexius, who recaptured Kastoria from the Normans with the help of George Palaeologus, starting from the area around Panagia Mavriotissa. The whole composition can be dated to after the Battle of Pelagonia, between 1259 and 1264. It a visual eulogy, designed to connect Michael Palaeologus to the Comnenus family. In the drum of the old, walled up entrance in the south wall there is a depiction of the Virgin Mary with the Christ-child reclining, with Saint Peter to the left.