View of the chapel vaulting

Four monumental figures are seated on clouds against a vibrant lapis lazuli sky scattered with golden stars. Each Evangelist is identified by a winged companion from the Tetramorph: Matthew with an angel, Mark with a lion, Luke with an ox, and John with an eagle. The figures are framed by heavy architectural ribs that meet at a central decorative boss, creating a sense of divine order within the chapel space.

This depiction of the Tetramorph represents the harmony between the four Gospels and the cosmic structure of the universe, a concept that linked theology to the four elements and the cardinal directions. In the Neoplatonic and Hermetic currents of the early Renaissance, such imagery illustrated the 'quaternary'—the fundamental numerical structure through which the divine Word manifests in the physical world.