Central mosaic panel of the Chapel of Saint John the Baptist, which represents the Baptism of Christ in the river Jordan. Highlighted by a background of clouds across a blue sky, we find the figure of the Father and the Holy Spirit, flooding the entire composition with light. The two major figures in the scene, Jesus and St. John the Baptist, are accompanied by the Virgin Mary, and an angel kneeling as to witness the Mystery. Two other panels on the side wall show biblical scenes, namely The Annunciation of the Angel and the Pentecost, and are remarkable for the nuances and for the sense of perspective.
The mosaics (tesselae) used in the panels were produced by the Italian mosaicist Alessio Matiolli. The models for these panels were made by Agostino Masucci (1691–1758), and the mosaic panels by Mattia Moretti (died 1779).