The Cathedral of San Lorenzo stands beside the Papal Palace on the highest point of the medieval city, its black-and-white striped Romanesque campanile visible from most of the old town. Founded in the 12th century, the building was substantially reworked in subsequent centuries; the current facade is a 20th-century reconstruction following World War II bomb damage, but the interior preserves its medieval character with a single nave and notable artworks.
The cathedral treasury holds the cofia of Pope John XXI — the skullcap worn by the only Portuguese pope when he died in Viterbo in 1277 after the ceiling of his apartments in the Papal Palace collapsed on him. The cathedral itself contains the tomb of Pope Alexander IV, who died in Viterbo in 1261.
The piazza in front, flanked by the Papal Palace loggia on one side and the cathedral on the other, is one of the most atmospheric medieval spaces in central Italy.