I visited this tentative WHS in July 2013. It is a great day trip away from Florence. There are several fortifications, squares, towers, clock towers, cathedrals and churches to explore but my personal favorites were the Torre Guinigi (with trees growing on top) and the San Michele in Foro Church. Piazza Anfiteatro should not be missed too. It is quite similar to Modena but has much more to offer in my opinion!