The baptistery of San Giovanni Battista stands in front of the Cathedral of Santa Maria del Fiore, in Piazza San Giovanni. Dedicated to the patron saint of the city of Florence, it has the dignity of a minor basilica.
Initially it was located outside the circle of the walls, but was included, together with the cathedral, in the walls built by Matilde di Canossa. It is currently located between Piazza del Duomo and Piazza San Giovanni, between the cathedral and the Archbishop's palace, in the religious center of the city. The main facade of the octagonal building faces east, towards the dome, while the apse faces west.
The Florentine baptistery was a place of investiture of knights and poets, as Dante Alighieri recalls in Paradise (XXV, 7-9). It was the seat for solemn oaths, as well as for the celebration in honor of the city patron with the gift of fine fabrics (the palios) by the magistrates of the Commune on the Baptist's anniversary.
The origins of the monument are one of the most obscure and discussed themes in the whole history of art. Until the sixteenth century the ancient Florentine tradition was followed, according to which it was originally a temple of the god Mars, modified in the Middle Ages only in the apse and lantern. In the following centuries, however, this idea was gradually abandoned, also because at the end of the nineteenth century excavating under the building appeared the remains of Roman domus, probably of the first century AD, with mosaic floors with geometric motifs.