Its interior preserves very important works of art: on the left side we find the first two detached frescoes showing the "Condottiero Giovanni Acuto"and "Niccolò da Tolentino" painted respectively by Paolo Uccello in 1436 and by Andrea del Castagno in 1456. Paolo Uccello also frescoed the clock on the inside wall, showing four vogorous "heads of saints".
The many sculptures made specifically for the cathedral (many of which have now been moved to the "Museo dell´Opera del Duomo"), comprise also the "Lunettes" by Luca della Robbia above the doors of the Mass Sacristies. The large "Pietà" by Michelangelo (c. 1553) has instead been removed and transferred to the "Museo dell´Opera del Duomo".
Most of the splendid stained glass windows were made between 1434 and 1455 to the designs of famous artists like Donatello, Andrea del Castagno and Paolo Uccello. The wooden inlays on the Sacristy´s cupboards were designed by Brunelleschi and other artists, including Antonio del Pollaiolo.
The internal walls of the dome, which have recently been restored, were frescoed between 1572 and 1579 by Giorgio Vasari (1511-1574) and Federico Zuccari (c. 1990-1609) who represented a large scene of the "Final Judgement".
The bell tower by Giotto remains, together with the huge dome one of the most striking views of the town. The famous painter, Giotto, was in fact also the architect of the project for the bell tower, although by the time of his death (1337) only the lower part had been completed. The works continued under the direction of Andrea Pisano (c. 1290-1349) and Francesco Talenti (not. 1325-1369) who completed the project.