The ancient Gothic choir was transformed in Baroque style between 1536 and 1540 following the design by Antonio da Sangallo the Younger and commissioned by Alessandro de’ Medici, the Duke of Florence, who intended to place the tombs of the two Medici Popes there. In the first years of the 17th century the choir was modified by Giovanni Fontana and subsequently by Carlo Maderno. The Baroque additions were removed during the 19th century restoration that restored the Gothic appearance when the polychrome stained-glass windows.