The Torrazzo is Europe’s highest medieval bell tower in brick: 122.217 meters high, it is sports a double-barrel construction consisting of two towers, one inserted in the other; a staircase of 502 steps runs in the cavity. Externally the tower is divided into two parts that allow one to read the stylistic episodes: the lower part, with a square base, on whose construction period there is no reliable data, is marked by a series of planes marked by frames decorated with intertwined blind arches, on which rest the openings of made up of monofora, bifora, and quadrifora leading to the terminal loggia; the upper part consists of the garland, built between 1284 and 1305 in Gothic style, created by the superposition of two octagonal drums, scaled and marked by round arches and by the conical cusp.

The astronomical clock, a true mechanical masterpiece, was begun in 1582, the year of the Gregorian reform of the calendar, by Giovanni Francesco and Giovanni Battista Divizioli, while the decoration of the clock face was entrusted to the painters Giovanni Battista Dordoni and Martire Pesenti. A series of repaintings followed through the course of the centuries, up to the most recent necessary restorations (1974), for the mechanical part Vincenzo and Pietro Ferraroni; for the astronomical calculation Achille Leani; and for the decorative part – the zodiac band – Mario Busini. The documents also nominate Janello Torriani (1550-1585), a famous Cremonese mathematician and inventor, as curator of the clock. He was a builder himself of several automatic and mechanic watches for the Emperor and King of Spain Charles V.