The Baptistery of San Giovanni, an expression of religious and political values of the city of Florence and one of the most important Italian monuments, is a wonderful anthology of marble and stone, mosaic and bronze, of the great Florentine art. The origin of the temple, dedicated to St. John the Baptist, patron of the city, is still uncertain, although you can perhaps attribute it to the IV-V century. C. Tradition says that it was founded in Roman times and dedicated to the god Mars. The building with its octagonal structure, the two lower orders, the attic and the dome belongs to the very early Christian architecture. In the ninth century, it performed the functions of the cathedral, again consecrated like Bishop’s house in November 6, 1059 by the Florentine Pope Nicholas II, newly elected. It is likely that on this occasion the temple was renovated or rebuilt. Certainly in this moment the pyramidal dome in eight segments was completed, while on the west side stood a semicircular apse to house the altar. Matching the three cardinal points the doors open, while the western part is closed from the apse. Only in 1128 St. Giovanni abandons forever the rank of cathedral and becomes baptistery. Between the mid-twelfth century and the thirteenth century was built the outer jacket with a classic taste geometric design made up of inlays in white Carrara and green Prato marbles. Also in the thirteenth century the apse change from a square into a semicircular apse, and the interior decoration of mosaics cover the pouch (about 1225-28), the entire dome (about 1270-1300), and the marble floor appears. The baptistry become the laboratory for the new Florentine school of painting that from Coppo di Marcovaldo and Cimabue, active in San Giovanni, will lead to Giotto. The exterior is embellished by three bronze doors: the oldest (1330-1336) is to the south, by Andrea Pisano, depicting the Stories of the Baptist. The north gate (1401-1424), block peat, is a work of Lorenzo Ghiberti, as well as the masterpiece of the East Gate (1425-1452), known as the paradise door, that depict the stories of the Old Testament.