An iconic example of the city's industrial architecture, this wool mill is located in Viale Galilei, along the Bisenzio River, where many major factories were built at the end of the 19th century. Originally there were two buildings, the first of which, now gone, was erected following the arrival of the railway in the city at Porta Serraglio, with a track transporting goods directly inside the factory. The imposing facade of the wool mill stands out in Viale Galilei with a great arched entrance, surmounted by the clock's stone molding, and a beautiful wrought-iron gate, which at the top bears the company’s initials surrounded by elegant floral decorations. The factory's courtyard still holds a large water tower, an indispensable element for the wet processes typical of the textile industry. The management of the Metastasio Theatre recently commissioned the writer Dem to paint on the walls of the former Calamai factory the polyptych "Observing the world through the eyes of others", a work that reflects the complexity of the city of Prato and at also refers to shows staged by the theatre.
The district outside of Porta al Serraglio started developing around 1880, foreshadowing the development along via Bolognese and the river, and was stimulated by the construction of the major factories - il Fabbricone, Lanificio Mazzini and the two sites of the Calamai factory - that played an important part in generating the future urban fabric. Construction of the wool mill began in 1924 and the factory appeared in the 1934 update of the IGM (Military Geographic Institute) maps. The factory was designed by the engineers Poggi and Gaudenzi, as shown by several plaques in the walls of the buildings reading: "Ing.ri Poggi Gaudenzi & C. Società per Costruzioni cementizie, Firenze via de' Martelli 7".