The interior of the church has a typical Greek cross layout, being a cross with arms of equal length. Each arm is roofed by a dome, with the largest dome at the centre of the cross; all the domes rest on a complex system of semicircular vaults supported by massive piers. The basilica’s initially plain decoration of columns, capitals and marble panels was elaborated upon by the order of Doge Vitale I Michiel (1156-1172), who initiated an ambitious programme of mosaic decoration.