The original Romanesque basilica church, built in the 9th century, as a shrine for the saint's bones, was destroyed by fire in 967. Byzantine architects assisted in its reconstruction, the main fabric being completed c.1071. In the 12th and following centuries through alterations and elaborate adornments it became a splendid Byzantine monument, reflecting Venice's preeminent position in trade with the East. In the 14th century, the facade received Gothic additions. The present structure is thus a mixture of Byzantine and Gothic and incorporates materials taken from temples and Eastern ruins. Its plan is a Greek cross , and it consists of a group of five square spaces, covered each by its pendentive dome. Each dome is consequently the center of a cruciform space, the wings of which have barrel-vaults . The only exception is the east end, where an apse is substituted for this space, and out of this apse spring three minor ones. Each dome is about hemispherical above its pendentives, and is pierced with windows. Its peculiarity lies in the breadth strips of the barrel-vault which support and separate this domes, which is so great that the vast piers which sustain them are pierced in two storeys, and divide each other in to four piers, with a vaulted space between them. The central dome is the larger than the others; it is 42 feet in diameter and the other four are each 33 feet. Inside, the central dome rises nearly 100 feet above the cathedral floor.
The domes are now covered by lofty dominical towers of timber, each surmounted by a sort of turret on its apex. The wings, which flanked each domed space, bounded as they were by the perforated piers, were so suggestive of side aisles that the builders added arcades from pier to pier, both in the nave and transepts . These are decorative, serving as narrow communications between the upper chambers in the great piers. .
The ground plan has numerous chapels and several rooms, which are appended to the transept.
