One of the most distinctive features of the square is the Cathedral’s bell tower, situated several yards from the cathedral itself, a thing uncommon outside of Italy. According to many scholars, the tower was in fact one of the towers of the ancient city walls of the mediaeval Lower Castle that once stood near the modern square. According to another version, not supported by modern historians, the base of the tower was in fact a small pagan temple, demolished and then turned into the bell tower. Regardless of its origins, the lower parts of the tower are mediaeval, with several small loop-holes preserved. Its oldest underground square section was built in the 13th century on the bottom of the old riverbed. Upper parts of the tower were added in the 18th century while the neo-classical finish was added in the 19th century, during the reconstruction of the cathedral.
It is a shame that I do not have the tower and the cathedral put together in the same photo as it was difficult to photograph both because of their difference in scales.