The church of the Archangel lies in the south part of Kastoria, in the cathedral parish, a short distance from Omonia Square. Reused architectural members such as columns, mullion bases and imposts indicate that the church was probably built on the site of an Early Christian basilica .

From an architectural point of view the church is a 9^th -10^th century basilica with narthex . On the inside, two colonnades divide it into three naves; the central one ends in a semicircular conch , while the side naves end in smaller conches built into the thickness of the wall. The raised nave has a barrel vaulted roof. The north nave was later expanded and doubled in width, but still retains part of the eastern wall and the conch.  An oblong narthex was added to the west of the church, covered by three vaults that divide the roof into three sections corresponding to the tripartite division of the nave.

On the interior there are two successive layers of decoration. All that survives of the first are a few poorly preserved fragments. Christ is visible in the apse of the north nave and Matthew the Evangelist in that of the south nave, added to which is a decorative band in a section around the sanctuary apse. Over the entrance to the narthex in the east wall, parts of a broader depiction of Advent show an imposingly large figure of an enthroned Christ opposite Abraham, Isaac and Jacob, the three forefathers. Saints are depicted in the arches, while the space over the south nave entrance has a half-length depiction of Christ shown blessing. Although these fragmentary representations do not help us to draw conclusions about this layer’s iconographic programme, in stylistic terms they point to the first layer of wall paintings in Agios Stephanos and the early frescoes of Cappadocian churches.

The second layer dates to 1359 -1360. Surfaces in the central nave are devoted to scenes from the Dodecaorton and the Passion, alongside full-length depictions of saints. The second layer paintings follow the anti-classical tradition of contemporary churches in Kastoria and Ohrid, tending towards a flat, linear rendition of forms and expressiveness in movements.

The outer west wall frescos feature full-length depictions of Panagia Hodegetria (Our Lady of the Way) and Archangels Gabriel and Michael. At the foot of the Archangel Michael there are smaller scale depictions of King Michael Asen of the Bulgarians (1246-1256/7) and probably his wife Anna - not his mother Irene Comnena, as argued until recently. The frescoes on the outer south wall depict local officials and inscriptions dating to the 15th century, which provide important information on the area’s people, clothes and art.