San Petronio Basilica: The Church That Ticked The Pope Off

Dec 4, 2018 0 comments

Dominating the central square in the city of Bologna is one of the world’s largest church with a unique mismatched façade that has been intriguing visitors for centuries. The upper half is made of bricks, while the lower half is made of marble with intricately sculpted scenes from both the Old and the New Testament.

“They just ran out of money,” is the usual reply tourists get when they ask what caused the church façade to be left uncompleted. But lack of funds was only part of the problem.


San Petronio Basilica. Photo credit: RossHelen/

The Basilica of San Petronio, dedicated to the patron saint of the city, Petronius, was begun in 1390. It was not intended to be a church, but rather a public space—a civic temple. The word ‘basilica’ was originally used to describe any ancient Roman building where courts were held and official and public functions took place. These buildings usually had a door at one end and a slightly raised platform at the other, where the magistrate or officials sat. As the Roman Empire adopted Christianity, all major churches were constructed with this basic architectural plan, and the word ‘basilica’ became synonymous with church throughout Europe and the New World.

The Basilica of San Petronio was planned as a grand monument, and in order to make room for its hulking body, several buildings in the square were demolished, including at least eight churches and towers. Construction went on for several centuries, until the beginning of the 16th century, when the city decided that the Basilica needed to be bigger in order to reflect the city’s growing wealth and importance, which is still visible in the city’s architecture—noticeably the numerous skyscraper-like towers.

Related: The Towers of Mediaeval Bologna

In accordance with the city’s wishes, architect Arduino Arriguzzi designed a new model for the Basilica that resembled a Latin cross with a size that surpassed even the Saint Peter's Basilica of Rome, the greatest church of the Western Christian world. When news of the proposed Basilica reached Pope Pius IV, he became so jealous that he immediately ordered the construction of a new building just twelve meters away to prevent the Bolognese from realizing their dream. Completed within a year, this new building, the Archiginnasio, became the University of Bologna, and remained so until 1808 when the University was moved to another location.


Aerial view of San Petronio church. Photo credit: Claudio Divizia/

With no room to expand, Bologna’s megalomaniac dream of building the biggest church on earth was shattered. Even the facade remained unfinished because they couldn't agree on how to finish it. The roof of the nave and apse were completed only in 1663.

Even while unfinished, the Basilica of San Petronio is a monumental church with a footprint 66 meters across and length twice as long. Its vault reaches 50 meters high. It is the tenth-largest church in the world by volume, and the largest church built of bricks.

The Basilica's half-finished marble façade is decorated with works by famous sculptors such as Jacopo della Quercia, Aspertini and Alfonso Lombardi. The central door features sculptures by Jacopo della Quercia depicting prophets and stories from the Bible, as well as a Madonna with a Child, Saint Ambrose and Saint Petronius. These sculptures would later inspire none other than Michelangelo, who spent some time in Bologna as a young man. The façade also features sculptures by Properzia de’ Rossi, one of the rare female sculptors of the Renaissance.


Photo credit: inhomogeneous orange/

Prophet Mohammed in Hell

The Basilica of San Petronio also hosts a controversial artwork. One of the chapels has a large fresco made by the 15th century painter, Giovanni da Modena, depicting Prophet Mohammed in hell being tortured and devoured by a demon. The unflattering depiction of the founder of Islam is based on Dante’s Divine Comedy where the poet consigned Mohammed to the ninth circle of hell, a place reserved for religious schismatics. In the poem, Mohammad is portrayed as split in half, with his entrails hanging out, representing his status as a heresiarch.

The fresco in the Basilica has offended many Muslim fundamentalists. An Islamist terror group linked to al-Qaida even tried to blow up the Basilica in the 2000s, to erase the offensive fresco, but the plans were thwarted.



The prophet being devoured by the Devil.

Cassini’s Meridian

The Basilica of San Petronio also boasts of the longest indoor meridian line in the world, measuring 66.8 meters. It was laid in 1656 by the famous Italian astronomer Gian Domenico Cassini. A hole on the roof of the Basilica allows the sun to shine through and make an elliptical spotlight on the meridian marking the passing of days and seasons.

Using the meridian line at San Petronio, Cassini was able to measure the change in diameter of the Sun's disk over the year as the Earth moved toward and then away from the Sun. He concluded the changes in size he measured were consistent with Johannes Kepler's 1609 heliocentric theory, where the Earth was moving around the Sun in an elliptical orbit instead of the Ptolemaic system where the Sun orbited the Earth in an eccentric orbit.


The meridian line inside San Petronio Basilica. Photo credit: Joaquin Ossorio Castillo /

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