The Baptistery, known as the giesa dei puti (children’s church), occupies a space to the south of the basilica that was once part of the atrium and open towards the pier. It is now accessed from the church but originally the entrance from the small square better identified the three spaces into which the chapel is divided: the Baptistery Antechamber where the catechumens awaited the ritual of baptism, the Baptistery proper and the presbytery. There is much uncertainty about information prior to creation of the present day chapel in the first half of the 14th century at the behest of Andrea Dandolo, a highly cultivated humanist and a friend of Petrarch. He was first procurator of St. Mark’s and later Doge (1343-1354).
As for the transformation desired by Dandolo, some scholars have recently observed that the Doge’s intention, over and above giving the church a new Baptistery with rich mosaic decoration, must have been to celebrate his own person and his family: the Doge is depicted as an offerer at the foot of the great crucifixion. The Baptistery mosaics are the last expression of the Venetian-Byzantine school, already evincing certain Gothic features.
The mosaic decoration centres on two themes: the figure of John The Baptist and the sacrament of baptism, a means of salvation brought to men by Christ.
On the Baptistery Antechamber barrel vault ceiling are the figures of the Old Testament prophets. On the walls below there are episodes from Jesus’ childhood interwoven with those from the life of John The Baptist. The picture opposite the door shows the Baptism of Jesus in the River Jordan, modelled on Byzantine iconographic canons. These mosaics have a clearly instructional aim for those who were here awaiting baptism.
In the cupola above the baptismal font, added later to Jacopo Sansovino’s design, Jesus sends the Apostles out into the world to preach and to baptise. The places of Apostolic preaching are recalled in the inscriptions.
In the small presbytery cupola, Christ in glory among the new angelic hierarchies is depicted in accordance with an iconography very close to Byzantine influences. The stories of John The Baptist begin from the lunette on the right side with the Announcement to Zechariah, Zechariah’s Meeting with Elisabeth and theStories of St. John, continuing all the way along the walls and concluding on the left, above the door towards the church and in the next lunette, with the Dance of Salome and the Martyrdom of the Saint, two works of extraordinary beauty executed by the last Venetian mosaicists of the middle ages.