In the Old Sacristy of San Lorenzo, built by Filippo Brunelleschi (1377-1446) between 1422 and 1428, a fascinating representation of the sky over the northern hemisphere occupies the entire surface of the cupola above the scarsella. The fresco may have been painted by Giuliano d'Arrigo, known as Pesello, undoubtedly under the supervision of an astronomer, who may have been Paolo dal Pozzo Toscanelli (1397-1482). The scientific import of the representation is revealed by the extreme precision with which the celestial bodies are positioned. Appearing in gold against the blue background of the sky are the Moon, the Sun, Jupiter, Venus, Mercury and the main coordinates of the celestial sphere, while the personifications of some of the constellations are outlined in black with white highlights. The position of the planets shows that the painting represents the sky over Florence on July 4, 1442, evidently a date worthy of being recorded, and perhaps connected to the arrival of René of Anjou. This hypothesis is supported by the fact that an almost identical fresco was painted a little later in the Chapel of the Pazzi, a family linked to the Angevin sovereign by bonds of faithful friendship.