The Basilica of San Petronio is a minor basilica and church of the Archdiocese of Bologna. It dominates Piazza Maggiore. The basilica is dedicated to the patron saint of the city, Saint Petronius, who was the bishop of Bologna in the fifth century.
San Petronio is one of the world’s largest churches (the sixth largest in Europe): it’s 132 meters long, 60 meters wide and 45 meters high. Construction began in 1390, based on a project by architect Antonio di Vincenzo. Work on the basilica continued for centuries, with a second project presented in 1514 envisioning a building that would measure 224 meters in length and 150 meters in width, bigger than St. Peter’s in Rome.
The Basilica of San Petronio houses the longest indoor meridian line in the world, measuring 66.8 meters. Inlaid in the paving in the left nave, it was designed in 1656 by Italian astronomer Gian Domenico Cassini.