The Principi Chapel should be third sacristy in the Basilica of San Lorenzo, near presbytery and chorus.
The crypt was building in 1604 for Ferdinando I by some of the most important florentine arists as Buontalenti, Giovanni de’ Medici, Poccianti etc.
The crypt is under the Principi Chapel, it has octagonal form with marble decoration.
The Cappellone was finished about 1740 by Ferdinando and Giuseppe Ruggirei, and it is characterized by marble windows and angular pilaster. Artists planned a great cupola on the basis of Brunelleschi’s project for Santa Maria del Fiore but it was never finished.
New Sacristy is one of Michelangelo’s masterpiece and a prototype for all Mannerist architecture, but the artist left it unfinished and it was later completed by Vasari.
The stone ribbing in pietra serena stands out against the white plaster. Inside is one of the most beatiful Michelangelo’s sculptural monuments, the monument to Giuliano Duke of Nemours and the monumernt to Lorenzo Duke of Urbino, then the statues of Day, Night, Dusk and Dawn of the Vergin Mary with Christ Child.