Torre dell'Orologio

The first stone of the central tower was laid in 1496 to a design by Mauro Codussi, the Bergamasque architect responsible for several of Venice's earliest Renaissance churches. The clock-bearing block went up by 1499; the two flanking wings were added in the 1500s by Pier Lombardo and his sons. Together the building completes the north side of Piazza San Marco and frames the entry into the Mercerie, the medieval shopping street that has connected the Piazza to the Rialto since the 13th century.

The great clock itself — designed by the father-and-son mechanics Gian Carlo and Gian Paolo Rainieri of Reggio Emilia — was set going on the first day of February 1499. It was, at the time, the most complex public clock in Europe and one of the earliest mechanical clocks of any size in Italy. Restorations took place in 1757, 1857 and most recently in a five-year overhaul completed in 2006, which returned the original Renaissance gilt and tempera to the dial.

The dial shows the hour in roman numerals around the rim, the phase of the moon in the centre, and the position of the sun in the zodiac on a slowly turning blue enamel disc. Above it sits the Madonna; on either side, two doors that open only during Epiphany and Ascension week to release a procession of three mechanical Magi led by an angel with a trumpet — a piece of automaton theatre still performed twice a year.

On the roof: a bronze winged lion of Saint Mark on a star-strewn ground (recast after the original was hacked off by Napoleonic occupiers in 1797), and the two figures known as the Mori — older bell-ringer, younger bell-ringer — who strike the hour with hammers. They have been doing it since 1497 and have lost their original colour to weather; the local nickname comes from the dark green patina the bronze has taken on, not from any depiction of Moors.

The tour is the only way in, and worth it. You walk up through the mechanism itself — exposed gears, hand-cut teeth, lead weights the size of children — and out onto the roof at the level of the bells.