The Work
The dome mosaic of the Neonian (Orthodox) Baptistery in Ravenna (c. 450-458) is the most complete surviving Late Antique baptistery program in the Western church and one of the finest examples of early Christian mosaic art in existence. Its placement in a functional baptistery - every person being baptized would look up at the dome above them - made its theological program immediately and personally applicable: the mosaic shows not a historical event but the prototype of the sacrament the viewer is currently receiving.
Biblical Source
Matthew 3:16-17 - "As soon as Jesus was baptized, he went up out of the water. At that moment heaven was opened, and he saw the Spirit of God descending like a dove and alighting on him. And a voice from heaven said, 'This is my Son, whom I love; with him I am well pleased'" - provides the central image. The dome shows Christ in the Jordan River at its center, John the Baptist pouring water, and the dove descending.
Matthew 28:19 - "baptizing them in the name of the Father and of the Son and of the Holy Spirit" - provides the sacramental formula that the mosaic enacts: the baptism of Jesus is presented as the prototype of Christian baptism, with the Trinitarian manifestation at the Jordan modeling the Trinitarian invocation at every subsequent baptism. Romans 6:4 - "we were therefore buried with him through baptism into death in order that, just as Christ was raised from the dead through the glory of the Father, we too may live a new life" - frames the significance of what the neophyte looking up at the dome is undergoing.
Artist
The mosaicists responsible for the Neonian Baptistery are unknown. The program was executed under Bishop Neon of Ravenna (c. 450-475), who gave the baptistery his name. The style reflects the transition from the flatter, more hieratic Byzantine style toward the richer, more volumetric treatment of the Western Latin tradition.
Iconography
The central medallion shows Christ's baptism; surrounding it in a ring are the twelve apostles in procession carrying crowns toward an altar - the baptized neophyte joining the apostolic procession. Below this ring, between the windows, stand alternating altars with open Gospel books and empty thrones (the hetoimasia, the prepared throne of divine judgment). The program encodes the complete theology of baptismal initiation: the new Christian joins the apostolic community, approaches the prepared throne of judgment now through the mercy of baptism, and will ultimately stand before the divine presence in the heavenly court. Looking up at the dome in the moment of baptism, the new Christian sees their entire theological reality in a single glance.