Basilica di San Petronio

The basilica is dedicated to Saint Petronius, bishop and patron saint of Bologna, and it is not the cathedral: the city council wanted it, not the bishop. Work began in 1390 to a design by Antonio di Vincenzo and continued for centuries. The project was so ambitious that, legend has it, the pope had the Archiginnasio built alongside the church precisely to prevent it from surpassing St Peter's in Rome.

The façade remains unfinished: the lower part is clad in marble, above it the brick is exposed. The central portal is by Jacopo della Quercia, with stories from Genesis carved in the fifteenth century. Inside, three soaring naves and twenty-two side chapels, decorated by artists including Francesco Francia, Lorenzo Costa and Parmigianino.

The Cappella Bolognini, known as the Chapel of the Magi, is the most famous: Giovanni da Modena frescoed it in the early fifteenth century with Paradise and Hell, an enormous Lucifer devouring the damned. In the music chapel there is an organ built around 1470 by Lorenzo da Prato, the oldest in the world still in use.

Along the floor of the left nave runs the meridian line of the astronomer Giovanni Domenico Cassini, completed in 1657: it is 66.8 metres long, one of the largest in the world. At true noon a ray of sunlight enters through a hole in the vault and falls on the brass line, marking the day of the year.