Complex sentence: The Basilica of San Petronio is the main church of Bologna, the old "città d'arte" in the Emilia Romagna region of Italy; however, it is not the metropolitan cathedral of the city, which is the Cathedral of Saint Peter.It dominates the Piazza Maggiore.
Split into simpler sentences: The Basilica of San Petronio is the main church of Bologna, the old art city in the Emilia Romagna region of Italy. It is not the metropolitan cathedral of the city, which is the Cathedral of Saint Peter.It dominates the Piazza Maggiore.