The exterior of the basilica is faced with polychromemarble panels in various shades of green and pink bordered by white and has an elaborate 19th-century Gothic Revival façade by Emilio De Fabris. The basilica is one of Italy's largest churches, and until development of new structural materials in the modern era, the dome was the largest in the world. It remains the largest brick dome ever constructed.
Grand Duke Cosimo I de' Medici decided to have the dome painted with a representation of The Last Judgment. This enormous work, 3,600 metres² (38 750 ft²) of painted surface, was started in 1568 by Giorgio Vasari and Federico Zuccari and would last till 1579.