This bright and spacious basilica consists of a single four-bay nave with cross-vaulted ceiling bordered with patterns of crosses and leaves, a transept and a polygonal apse. The four ribbed vaults are decorated alternately with golden stars on a blue background and paintings. The second vault is decorated with roundels with busts of "Christ" facing "Saint Francis" and the "Virgin" facing "Saint John the Baptist". The entrance vault gives us the "Four Latin Doctors of the Church": St Gregory facing St. Jerome and Saint Ambrose facing St. Augustine. These are ascribed to the Isaac Master.