It has a rectangular plant, with an external facing wholly composed of marble, laid in polychrome bands. The exterior appearance is marked by cusps, tympani and tabernacles, together with a complicated sculpture decoration with tarsiae, rose-windows and numerous statues from the main Pisane artists of the 14th century. These include Lupo di Francesco, Andrea Pisano with his sons Nino and Tommaso, and Giovanni di Balduccio.
