You may see Cagliari Cathedral Museum from a distance before you actually find this grand building. Look around inside if it's open or just appreciate the facade from the street.
You'll soon learn why this Cagliari principal church is a hit with travelers. If you're searching for more to see and do here, Bastion of Saint Remy, National Archaeological Museum, and Roman Amphitheatre of Cagliari are in this area too. They won't take you very long to reach from Cagliari Cathedral Museum.