 The interior houses important works of art.The oldest are the frescoes of the "Stories of Abraham, Isaac, Jacob and Joseph" in the southern and northern transept vaults (late 14th-early 15th century).Also from the Renaissance are the arch of the "Stories of the Martyrs Marius and Marta, Audifax and Habakkuk", martyrs in Persia (best known as "Arch of the Persian Martyrs", 1482), and the relief of Saint Himerius (1481-1484), both works by Giovanni Antonio Amadeo.