In the center of the building stands the baptismal font, where the sacrament of Baptism is administered, the sacrament of initiation into the Christian faith. The vat serves to contain the water sanctified by the Holy Spirit by which Christians become adopted children of God. When Jesus, the Son of God, presented himself to John the Baptist to be baptized by him, in his immersion into the water of the Jordan River he reiterated his will to enter into the poverty of the human condition, opening up to mankind access to divinity.
The font, made between 1416 and 1434, has six sides, recalling the six days of Creation, because Baptism makes the recipient ‘a new creature.’ The base, composed of two marble steps, bears inscriptions taken from the Gospels concerning the baptism exercised by John the Baptist and Christian baptism. Placed on the outer corners of the vat are statues personifying three of the cardinal Virtues (Justice, Prudence, and Fortitude) and the three theological Virtues which are the gift of the Holy Spirit (Faith, Hope, and Charity). Between them are beautiful panels illustrating key moments in the life of Saint John the Baptist.
Above the vat is the tabernacle of the Chrism, used to hold the Holy Oils for the anointing which concludes the rite of Baptism. In the outer niches are five statues of prophets, because John is considered the last of the prophets who announce the coming of the Messiah; for this reason, on top of the font is the bronze effigy of the Baptist.
Some of the most important artists of the time took part in the making of this early Renaissance masterpiece: Donatello, Lorenzo Ghiberti, and Jacopo della Quercia.