You'll probably spot Susa Cathedral from a distance before you actually find this grand religious building. Take a seat inside if it's open or just admire the facade from outside.
You'll soon find out why this Susa principal church is popular with travelers. If you're searching for other things to keep you busy, Abbey of Novalesa, Exilles Fort, and Roman Amphitheater are in this area too. They won't take long to reach from Susa Cathedral.