Michelangelo was commissioned in 1516 by Pope Leo X to build a splendid façade for the Basilica of San Lorenzo. The Medici church had become increasingly important with the rise to power of the Medici family and the Medici pope, Leo X. In 1516, Michelangelo returned to Florence to carry out this politically important commission for this Medici pope.
The artist labored on the project, declaring with uncharacteristic pride that the façade would be a "mirror of architecture and sculpture of all Italy." Then, after Michelangelo had invested three years and countless trips to Carrara and Seravezza in search of the perfect blocks of marble, the commission was canceled and the project abandoned without the pope giving an explanation to the furious and humiliated artist.
One possible reason for the abandonment of the commission was the death in 1519 of Lorenzo de' Medici, the church's namesake and the driving force behind the project. To this was added the Medici desire to fund another Medici family monument, a tomb chapel for two Medici dukes, the above-mentioned Lorenzo and Giuliano (died 1516).
While working on the Basilica di San Lorenzo, Michelangelo also found time to do additional work for the Medicis. Read about his windows for the Palazzo Medici-Riccardi next.