 The original building plan was a Greek cross with a grand cupola at the crossing, but today the plan is a Latin cross with a central nave flanked by two side aisles on each side, with the apse and transepts having three naves.The inside offers a spatial effect similar to that of the great mosques thanks to the use of raised lancet arches, the alternating layers of black and white marble, and the elliptical dome, inspired by the Moors.The presence of two raised matronea in the nave, with their solid, monolithic columns of granite, is a clear sign of Byzantine influence.