 In the Torrazzo's fourth storey resides the largest astronomical clock in the world.The mechanism was built by Francesco and Giovan Battista Divizioli (father and son) between 1583 and 1588.The exterior, originally painted by Paolo Scazzola in 1483 but later repainted many times, including by Giovanni Battista Dordoni, represents the sky with zodiac constellations and the Sun and Moon moving through them.