 The exterior has bichrome marble bands which re-use Roman stones.The façade, designed in the 12th century, but completed in 14th maybe by Giovanni Pisano, has two corps with pilaster strips, blind arches, marble intarsias and three orders of loggias in the upper section.The interior is on the Latin cross plan with a nave and two aisles divided by columns in granite from Elba, an apse and a dome on the crossing with the transept.