San Petronio is a prominent basilica located in Bologna, Italy. It is dedicated to the city's patron saint, Saint Petronius, and is known for its impressive Gothic architecture. Construction began in 1390, and the church features a striking façade made of brick and marble, along with a large interior that can accommodate thousands of visitors. The basilica is famous for its beautiful artworks, including frescoes and altarpieces by renowned artists. One of its notable features is the large sundial on the floor, which was designed by the astronomer Giovanni Domenico Cassini in the 17th century. San Petronio remains a significant cultural and historical landmark in Bologna.