It balances Filippo Brunelleschi's Sagrestia Vecchia, the 'Old Sacristy' nestled beside the left transept of San Lorenzo, with which it consciously competes, and shares its format of a cubical space surmounted by a dome, of gray pietra serena and whitewashed walls.

[6] Four Medici tombs were intended for the project, but those of Lorenzo the Magnificent and his brother Giuliano (buried beneath the altar at the entrance wall) were never begun.

The magnificent existing tombs are those of two more recently deceased and less well-known family members whose careers had been cut tragically short by their comparatively early deaths: Giuliano di Lorenzo, Duke of Nemours (d. 1514, aged 37) and his nephew (d. 1519, age 27) Lorenzo di Piero, Duke of Urbino, whose daughter Catherine de' Medici became Queen of France).

It was designed by Matteo Nigetti, following some sketches tendered to an informal competition of 1602 by Don Giovanni de' Medici, the natural son of Cosimo I, which were altered in the execution by the aged Buontalenti.

The art of commessi, as it was called in Florence, assembled jig-sawn fragments of specimen stones and porphyry to form the designs of the revetment that entirely cover the walls.