Example Illustrated: St. Mark’s Cathedral in Venice, Italy
See image with the large central dome, as well as four other domes over each of the arms of the Greek-cross floor plan on the interior. There are extensive mosaics inside and outside the structure (visible on the front in the photo above).
Another example: the Hagia Sofia in Istanbul, Turkey
After the move of the seat of the Holy Roman Empire from Rome to Byzantium in approximately 330 A.D., large churches with massive domes were built characterizing the Byzantine architectural style. The style was particularly used during the Justinian empire of the 6th century, and persisted in the following centuries eventually spreading to Greece and Russia with the Byzantine liturgy. The flow of the church is downward from the dominating central and ancillary dome structures as if Heaven is meeting Earth (“hanging architecture”). The churches frequently have a Byzantine-Greek cross floor plan with a central cross and arms of equal length. The large structures were ornamented with marble, inlay and mosaics.