The Cathedral or Duomo and the Baptistery of Florence stand in a huge rectangular area and occupy two separate but comunicating squares: Piazza del Duomo, which contains the basilica of Santa Maria del Fiore (the third largest cathedral in the world after St. Peter's in Rome and St. Paul's in London), and Piazza San Giovanni, with the Baptistery right in the centre, probably the first Christian church in the city, as it was built in late Roman times (4th-5th century A.D.?) on the ruins of what was possibly a Roman temple dedicated to the god Mars.

However, the Baptistery as we see it today, which has always represented an architectural reference point for Florentine artists, dates from the 11th-13th century, when the external revestmment of marble, the interior and the mosaics in the cupola were completed. The three famous doors in gilded bronze, including the so-called Doors "of Paradise", were cast at a later date, between 1330 and 1452.