Founded by the bishop Ursus, therefore after the year 396, it was built before the transferral of the capital from Milan to Ravenna. The baptistery, whose floor is dominated by a marble arch, is famous for the mosaics in the cupola commissioned by Bishop Neonius.
The mosaic series of the cupola has three bands.
The first band concentrates on the baptism of Christ, immersed to the waist in the waters of the River Jordan (personified by an old man). Standing near to Christ on the bank of the river, the Baptist administers the baptism.
The second band, which is the first large band that surrounds the medallion, represents the twelve apostles led by their respective leaders Peter and Paul. The apostles, masters and witnesses to the baptismal faith, proceed in stately procession with the triumphal crown of victory.
The third band, of great iconological value, represents the heavenly garden, the Kingdom of god and destiny for the neophytes baptised in this baptistery. It is a garden paradise where plants, birds and flowers triumph in refined and sensitive array. The four thrones correspond to four altars with the four gospels that, with the seats of the righteous, are extremely well-known symbols of Christian eschatology.
Band of the 16 prophets
Created in stucco, this band is of great importance. In fact the twelve apostles depicted complete the two Christian sources of faith (apostles and prophets) according to the affirmation “built up (the neophytes, new baptised believers) on the foundation of the apostles and the prophets with Christ Jesus himself as the chief corner stone (Letter to the Ephesians 2.20).