The Pazzi Chapel was commissioned to Filippo Brunelleschi by Andrea de' Pazzi in 1429, but it was never completed because the family suffered the consequences of the conspiracy organised against the Medici family by Jacopo and Francesco dei Pazzi. During the ambush, Giuliano dei Medici, the beloved brother of Lorenzo the Magnificent, was killed inside Florence Cathedral during mass on 26 April, 1478.
The chapel was used as a Chapter house, that is, a meeting place for the friars of Santa Croce. It has a rectangular floor plan consisting of a square room with an umbrella-shaped dome, that is, in segments. The back wall opens onto a small square apse covered by a small dome. The central dome is decorated with tondi and the Pazzi family coat of arms, two dolphins opposite each other made of glazed terracotta by Luca della Robbia. But the most distinctive feature is that the dome is decorated with a fresco depicting the sky of Florence on the night of 4 July, 1442, a fresco almost identical to the one found in the scarsella (small apse) of the dome in the Old Sacristy of San Lorenzo . The frescoes differ only in their change of position on the axis inside the building: both are like a modern photograph showing the same part of the sky, but observed from slightly different viewpoints. The frescoes of the starry sky undoubtedly precede the Pazzi Conspiracy. However, despite the great rivalry between the Medici and Pazzi families, these frescoes unite them in a mysterious date.