The Byzantine Greek-cross church, newly developed and standardized during the "second Golden Age" of Byzantine religious art (often called the Macedonian Renaissance for its ruling dynasty), features consistent mosaic programs, exemplified by the churches of Hosios Loukas in central Greece.

The centralized parallelogram-shaped church of the Theotokos, the oldest in the complex and the only church known to have been built in mainland Greece in the tenth century, is the oldest example of the cross-in-square type in the country; its plan closely follows that of Fenari Isa Cami in Constantinople.

The walls are opus mixtum (part brick, part stone, part marble) and display curious pseudo-kufic patterns.

The Church of the Theotokos adjoins a larger cathedral church, or the Katholikon, tentatively dated to 1011-12.

The Katholikon is the earliest extant domed-octagon church, with eight piers arranged around the perimeter of the naos.

The hemispherical dome (without a drum) rests upon four squinches which make a transition from the octagonal base under the dome to the square defined by the walls below.

The main cube of the church is surrounded by galleries and chapels on all four sides.