The square campanile, which rises above the the center of the church, was built in the years 1577 to 1593 and is attributed to Giacomo della Porta. The upper storey is just above the roofline, and has a tall and proportionally narrow arched and molded soundhole on each face. The top has a triangular pediment with modillions on each side, then comes a low square plinth followed by an octagonal one with an oculus (round opening) on each face. Finally there is the cupola, which is ogee-curved in lead with a ball and cross finial.