You needn't be of strong faith to enjoy the peaceful atmosphere of Colle di Val dElsa Cathedral. Check when the next mass starts or when it's open for general viewing.
Situated in Colle di Val d'Elsa, this principal church is worth including in your schedule. But you'll find tons more to see and do in the area. Collegiate Church of Santa Maria Assunta, Medieval Criminal and Torture Museum, and Piazza Duomo aren't too far away from Colle di Val d'Elsa Cathedral.