Duomo di San Martino
Romanesque cathedral dating to 14th century. Contains the must-see Volto Santo and Ilaria del Carretto's Sarcophagus Note you have to pay to see this - By Jacopo della Quercia. Includes a sculpture of the crucifixion attributed to an eyewitness, Nicodemus. Some interesting carvings in the marble exterior, including a labyrinth.