Baptistry
Unlike Florence or Pisa, Siena did not build a separate baptistry. The baptistry is located underneath the eastern bays of the choir of the Duomo. The construction of the interior was largely performed under Camaino di Crescentino and was completed about 1325.
The main attraction is the hexagonal baptismal font, containing sculptures by Donatello, Jacopo della Quercia and others.
Read more about this topic: Siena Cathedral