Interior view

The New Sacristy (Sagrestia Nuova) of San Lorenzo and the Biblioteca Laurenziana were singled out by Vasari as marking a conscious break with ancient and modern tradition in their use of licentious non-Vitruvian detail. Both projects were conceived by Cardinal Giulio de'Medici (later Pope Clement VII) in summer 1519, although the designs for the library were not produced for another five years. The New Sacristy was to house the tombs of the recently deceased Medici dukes Lorenzo of Urbino (d. 1516) and Giuliano of Nemours (d. 1519) - the Capitani - and their 15th-century forebears Giuliano (d. 1478) and Lorenzo de'Medici - the Magnifici (d. 1492).

The new chapel was to balance Brunelleschi's Old Sacristy (1421-28) opposite, and its exterior treatment matches the levels and detailing of the 15th-century transept. For the plan and interior elevation, Michelangelo's starting-point was also the Old Sacristy, but he introduced an intermediate level with tabernacle windows, arches and pilasters between the main order and the pendentive zone.

Work began in autumn 1519, and by April 1521 the first interior order was largely in place. In 1525 the exterior was crowned by the innovative marble lantern with its lively broken silhouette and faceted bronze ball, deliberately varied by Michelangelo from the 15th-century example on Florence Cathedral. The marble ornament of the interior was begun in 1524, with the construction of the tombs of the Capitani and the doors and tabernacles in the corners. The Magnifici tomb opposite the altar was never finished, nor was the sculptural programme, which remained incomplete when Michelangelo moved definitively to Rome in 1534.

The rapid development of Michelangelo's architectural language in these years can be traced in the successive elements of the interior architecture. The pietra serena articulation of the first two levels draws on Florentine tradition. Above the second cornice the more adventurous tabernacle windows with their upwardly converging frames show Michelangelo improvising from an antique motif.

In extending the sacristy upwards to bring in more light Michelangelo did not entirely succeed in unifying the interior space, which remains rather box-like and planar, but its wealth of invention in detail makes it a pioneering if awkward building.

View the ground plan and the section of Sagrestia Nuova, San Lorenzo, Florence.