Saint Mark’s Basilica was rebuilt starting in 1063 during a period of closer relations between Venice and Byzantium. It has five cupolas: three along the east-west axis and two on the transepts, on either side of the central cupola. The Greek cross plan is modelled after the sixth-century Church of the Holy Apostles in Constantinople, which makes it anachronistic in the history of Byzantine architecture. By the same token, the programme of mosaics does not correspond to contemporaneous Byzantine examples.
The interior decoration of Saint Mark’s is not uniform. It seems to have been produced mainly by local workshops that had come into contact with the Byzantine world. The first mosaics, in the eastern part of the basilica, were made in the late eleventh and early twelfth centuries. The decoration was completed only after Constantinople was taken in 1204.
The atrium, which in this context is a sort of gallery encircling the basilica to the west and north, is covered with six cupolas and two large vaults: two cupolas and vaults in the western arm, three cupolas in the northern arm and one cupola over the crossing of the two arms. The atrium was rebuilt in its present form only after 1204, which means that the mosaics date from a later time.
The theme of the decoration is Genesis, starting from the account of the Creation. The programme begins in the western arm at the southern end with the Genesis cupola, continues with the Flood vault, the Tower of Babel vault and the three cupolas of the life of Joseph, and concludes with a cupola depicting the life of Moses. The images on the barrel vaults between the cupolas and those on the five small apses in the northern arm represent more Old Testament scenes. All the images are set against a gold ground.
This programme is very similar to Byzantine iconography but the overall design and lay-out of the decoration do not match contemporaneous Byzantine productions. The programme is strictly Western.
The biblical episodes are based fairly accurately on liturgical readings from the lectionary of the Curia. The biblical readings for the seven Sundays between the Sunday of the Septuagesima and the fourth Sunday of Lent begin with the creation of the world in six days and continue with the episodes of Cain, Noah, the Tower of Babel, Abraham, part of the story of Isaac, and that of Joseph, concluding with the story of Moses and the Exodus from Egypt.
At the centre of each cupola is a different circle, richly decorated in bright colours. The vegetal, geometric and architectural motifs suggest borrowings from the Islamic rather than the Byzantine world.
The style dates back to examples from late Antiquity; a Bible that may have been copied and illustrated in Egypt between the fifth and sixth centuries could have served as a model, for instance. The style is similar to that of a manuscript called the Cotton Bible, which was almost entirely destroyed by a fire in the seventeenth century. Presumably that manuscript was in Venice in the thirteenth century and could have been used as a model for the Genesis mosaics.
Venice most likely wanted to compete with Constantinople, in particular by attempting to demonstrate its ancient roots while at the same time retaining its own specific characteristics and thereby assert its identity.
 Times of the liturgical calendar prior to the Council of Vatican II, corresponding to 70 days before Easter.
Demus, O. The mosaics of San Marco in Venice. 2: The Thirteenth Century. Chicago, London, 1984, the University of Chicago Press.
Demus, O., San Marco: die Mosaiken, das Licht, die Geschichte, Munich, 1993.
Lowden, J. “The Beginnings of Biblical Illustration in Imaging the Early Medieval Bible” in Imaging the Early Medieval Bible, University Park, 1999, Pennsylvania State University Press, p.9-59.