Reggio Emilia's cathedral anchors Piazza del Duomo and carries the marks of several centuries of rebuilding. Its origins go back to the early Middle Ages, but much of what you see today reflects later Romanesque, Renaissance, and Baroque changes.
It is worth stepping inside while crossing the historic centre, especially if you are already visiting nearby Piazza del Duomo, Sala del Tricolore, or the Basilica di San Prospero.