The western façade of the Cathedral was richly decorated, particularly on the walls and archivolts of the original portico, which we are able to recreate thanks to a very detailed description by the scholar Del Giudice. A mosaic, similar to the one in the central apse, was placed above the two central columns, depicting two archangels. Isaiah and Balaam were represented on the left and right respectively, accompanied by inscriptions. The three archivolts were decorated with five tondi depicting images of saints, while the interior features a cycle dedicated entirely to the Virgin Mary.