No matter if you're making a religious pilgrimage or just curious about what's inside, visitors are welcome at Duomo. Why not see if you can attend a mass?
This Castelnuovo di Garfagnana principal church is a good place to start your day of sightseeing. There's plenty to see in the area, such as Santuario Mariano Eremo di Calomini, Grotta del Vento, and Isola Santa Lake. Wander around at your leisure at Duomo before hitting up these other fine sights.