After long restoration work, the Clock Tower in Piazza dei Signori reopened in June 2010, housing the oldest functioning astronomical clock in Europe still in its original tower. It was built in 1344 by the famous engineer and astronomer Jacopo Dondi of Chioggia, and its account of the movement of the planets follows Ptolemy’s geocentric theory of the Universe.
Thirty metres high, the tower has five floors: the first three house the clock mechanism, the last two housed the accommodation of the Master Clocksmith, responsible for the maintenance of the astronomical clock. The clock itself has a so-called ‘bird-cage’ movement with the two ‘trains’: a timekeeping train and a chime train.
The clock face is circular and divided into concentric bands: the external band is inscribed with the numbers of the hours in Roman numerals; the middle band – made up of lead sheets – is decorated with copper stars; the third band contains relief depictions of the symbols of the Zodiac and at the very centre is the planet Earth.
One curious absence is that of a symbol for zodiacal sign of Libra. This is due to the fact that Dondi drew upon Roman accounts as his frame of reference, and in ancient times the sign of Scorpio occupied two months: one the body, the other the tail. The association of the sections of the tail with Libra would only come later.