The Medici Chapels were built as a personal sepulchre of the Medici family right in the basilica of San Lorenzo, the one considered by the Medici as their private church and located in front of the residential palace in via Larga (presently via Cavour). The cardinal Giulio de' Medici, the future Clemente VII, and Leone X, in 1520, involved Michelangelo Buonarroti in the project of the Sacrestia Nuova: or better of a chapel en pendant with the Sacrestia Vecchia by Filippo Brunelleschi, where distinguished members of the family would be buried. The works began in March 1520 and were definitely completed by Giorgio Vasari in 1546, after Michelangelo, in 1534, had left Florence directed to Rome.
The project provided that in the chapel would be placed the tombs of Lorenzo il Magnifico, of his brother Giuliano de' Medici, of Lorenzo the Duke of Urbino (Piero's son, the eldest son of Lorenzo) and of Giuliano the Duke of Nemours (the third son of the Magnifico): the two Magnifici and the two Capitani. Only the tombs of the Capitani were completed. On the left of the altar is the sepulchre of Lorenzo Duke of Urbino, whom, in the act of reflecting, was defined by Vasari as il Pensieroso (the thoughtful), and it is, thus, identified by the critics as the symbol of contemplative life: beneath him are, set over the volutes of the sepulchre, the symbolizations of il Crepuscolo (dusk), characterized in the face by the famous uncompleted typical of Michelangelo, and l'Aurora (dawn), of which the plastic force reveals the interest cultivated by the artist towards anatomical studies.
In front of it is the sepulchre of Giuliano, the symbol of active life, with the swagger-cane in his hand: and underneath it il Giorno (the Day), in a un motion of rebellion, and la Notte (the Night), inspirer on the other hand of very famous verses written by Michelangelo. In the Brunelleschi style architecture - because of the duotone of the grey stone with the white plaster - Tolnay interprets it as the subdivision of three spheres: the sphere of the Hades, the earthly one and at last the celestial sphere culminating with the cupola - inspired by the Pantheon's. While on the other hand the sepulchres would allude to the concept of the soul free from the earthly commitments and tending towards the contemplation of the divine life incarnated by the Virgin. This statue - created by Michelangelo in 1521 and placed above the sarcophagus of the two Magnifici - represents, in fact, the spiritual mainstay of the Chapel and is surrounded by the statues of the two patron saints of the Medici family: on the right Cosma, produced by Montorsoli (1537), and on the left Damiano, created by Raffaele da Montelupo (1531).