The Battistero di San Giovanni – or Baptistery of St. John – is the building that completes the considerably striking appearance of the cathedral’s square. It has three famous doors, sumptuously decorated, and was used in the past for the investiture of knights and poets. The near Museo dell’Opera del Duomo houses works designed and built for the Cathedral of Santa Maria del Fiore, the Bell Tower and the Baptistery.

The Baptistery of St. John is characterised by an octagonal plan, lined with a dome of eight segments, and covered by a pyramid roof. The outside is decorated with white marble from Carrara and green marble from Prato, both characteristic materials of Florentine Romanesque architecture.