To have lunch, we recommend having a slice of pizza at the La Trofea pizzeria, in the Piazza del Campo which leads off the Via Rinaldini. They are delicious! 2.50€ per slice.
If you would rather sit down, you can try the Pizzería di Nonno Mede, in Camporegio street, number 21. Very popular with Italians, they have mouth-watering pizzas for 5-6€ and fantastic views of the Duomo.