The mosaics in the church of Santa Prassede were commissioned by Pope Paschal I (r. 817-24).
In the centre of the mosaic in the apse stands Christ. His head is surrounded by a halo with a blue cross; above, the hand of God the Father emerges from the clouds to crown him. To Christ’s right stands St Paul (the only figure whose tunic carries a monogram), St Praxedes and Pope Paschal I, while to his left we see St Peter, St Pudenziana and St Zeno. The pope, whose monogram may be seen in the centre of the two arches, appears in the apse mosaic holding a model of the church. He sports a square nimbus, indicating that he was alive when the mosaic was created.
A phoenix, a symbol of birth and rebirth, sits on the branch of a palm tree. Below the feet of the seven figures flows the river Jordan. Standing on a small mound, in the centre of the lower part of the mosaic, is the Agnus Dei (Lamb of God), under whose feet flow the four rivers of paradise. The sheep, to either side, symbolise the twelve apostles, while the walled cities at each end represent Bethlehem and Jerusalem.
In the centre of the outer wall of the apse, the Lamb of God sits on a throne, under which is the book 'sealed with seven seals' (Revelation: 5:1). To left and right are the 'seven golden candlesticks' (Revelation: 1:12). These, in turn, are flanked by four angels and four winged creatures, the symbols of the four Evangelists (Revelation: 4:7). At a lower level are the 'four and twenty elders sitting, clothed in white raiment; and they had on their heads crowns of gold' (Revelation: 4:4).
In the centre of the triumphal arch is an image of the Heavenly Jerusalem. Within its walls are the twelve apostles, with St John the Baptist and Mary on the left and St Praxedes on the right. In the upper left hand corner of the city is a figure holding up a scroll with the word ‘LEGGE’ (Read). Outside the walls are bands of martyrs waiting to be admitted. Below this composition, on either side of the arch, are two groups of people. Holding crowns and palm branches, they are the multitude of the martyrs. The mosaics were seriously damaged in the 16th century when relic cupboards were inserted into the walls.