The Duomo’s side walls are simply decorated with local basalt stone and white travertine.
The interior of the Cathedral is very spacious and neat. Its walls are like the exterior one adorned with travertine and alabaster. During the 19th century the top part of the walls were painted in black and white.
Throughout the 16th century many frescoes were covered with stucco.
The Chapel of the Corporal was built between 1350 and 1356; it houses the corporal of the miracle of Bolsena and the tomb of Pietro Parenzo a city’s major who was murdered in 1199.