The two faces of the Basilica of San Petronio in Bologna

Basilica di San Petronio
Antonio di Vincenzo
Bologna, Italia
44° 29′ 34″ N, 11° 20′ 37″ E

The Basilica of San Petronia in Bologna is a huge religious basilica of Gothic architecture which has the specificity of being made of brick with only half of its facade in marble. The basilica is dedicated to the city’s patron, saint Petronius. It was not consecrated until 1954 although its works began in the end of the 14th century.

The architecture of the basilica is closely linked to the history of Bologna and its political and cultural position in what was then the Holy Roman Empire. In mid 12th century Italy, two factions clashed and opposed each other militarily, politically and culturally: the Ghibellines and the Guelphs. The former supported the Empire while the latter supported the Pope. Their conflict began after the death of Henry V, who left no heir. The papists installed Lothair III, but at his death the imperials triumphed and regained power. A succession of power struggles followed over several centuries, exacerbated in some cities like Florence or Genoa by dynastic family quarrels.

Bologna, Basilica San Petronio and Piazza Maggiore - Steffen Brinkmann
Bologna, Basilica San Petronio and Piazza Maggiore
The Bologna history of conflict with Papal Authority

In 1274, the city of Bologna expelled the Ghibellines, however internal struggles weakened the city. The city came under papal authority and then became independent to finally become a signoria in 1334. Later, the city came into conflict with the papacy by allying itself with Florence (1375-1378) before coming back under the authority of the pope at the end of the 14th century.
Following this restored order and the victory of the Guelph faction, the city decided to equip itself with a new civic and religious place, a temple for the city. The Consiglio Generale dei Seicento prepares from 1388 the construction of the church. Several churches and municipal buildings were destroyed to make way for the large-scale project. The project of the church is dedicated to Petronius (5th century) who became officially a saint and protector of the town in 1253.

Ground plan of the San Petronio Basilica with the Cassini's Great Meridian line
Ground plan of the San Petronio Basilica with the Cassini's Great Meridian line
The long construction of the basilica

The first stone of Antonio di Vincenzo’s project was laid in 1390, but the work lasted a long time. The successive political crises, the size of the project, the lack of materials and economic means, all these factors made the construction spread over several centuries. For example, the side chapels begun in 1393 but were completed in 1479. The decoration of the central nave was completed in the 17th century, marking the end of the construction.

The San Petronio Basilica is one of the last Gothic religious buildings of medieval Italy. It is 132m long, 60m wide and its vault is 45m high. Its dimensions make it the largest Gothic brick church in the world, capable of accommodating 28,000 people. Its facade, facing Piazza Maggiore, is the main specificity of the basilica, the witness of its eventful history. It is 51m high and is divided into two horizontal bands. The first one, the lower one, is made of marble and was built between the 14th and 16th century. The upper part, like the rest of the church, is made of bricks, ready to receive its marble covering. The initial design was made by Domenico da Varignana and the construction started in 1538 by Giacomo Ranuzzi.

Political and religious conflicts and their architectural consequences

Both sides of this facade are justified by a lack of funds. This can of course be explained by the longevity of the work and the size of the building, as well as the political situation in the city. But the relations of the city with the papal authority are also a reason. The project of the basilica was initially intended to make it the largest church in the world, and to surpass the St. Peter’s Basilica in Rome, which was out of the question for the papal authority.

As soon as di Vincenzo died in 1402, the legate of Pope Baldassare Cossa, sworn enemy of the city, sold stones, wood and all building materials. Later, Pope Pius IV decided to build the surrounding buildings as a priority. In 1562, the Archiginnasio was built in record time, financed solely by papal funds. The building, situated 12m from the basilica, prevents any extension of the church and in particular prevents it from having its characteristic Latin cross plan. These papal interests linked to the successive changes of power and the cultural spirit of the city have given this aspect to the basilica. The facade, divided in two, is the best representative of its history.

At the time of its construction and especially during the fifteenth century, many projects were proposed (notably by Palladio) to develop this facade, before finally deciding that it would remain as it is today.

First facade project suggested by Baldassarre Peruzzi in 1522
First facade project suggested by Baldassarre Peruzzi in 1522
Source: Heritage Times (with interiors photos), Images from Wikicommons

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