Petronius was bishop of Bologna during the fifth century. He is a patron saint of the city. Born of a noble Roman family, he became a convert to Christianity and subsequently a priest. As bishop of Bologna, he built the Church of Santo Stefano.

Bologna is the capital and largest city of the Emilia-Romagna region in Northern Italy. It is the seventh most populous city in Italy, with about 400,000 inhabitants and 150 different nationalities. Its metropolitan area is home to more than 1,000,000 people. It is known as the Fat City for its rich cuisine, and the Red City for its red tiled rooftops and, more recently, its leftist politics. It is also called the Learned City because it is home to the oldest university in the world.