After the fall of the Empire, this area fell under the power of Odoacre, Theodore the Great (493-526), Byzantium and finally the Longobards, who used it mostly as a military centre. In 774, the city fell to Charlemagne, who gave it to Pope Adrian I.
In the 11th century, Bologna began to aspire to being a free commune, which it was able to do when Matilda of Tuscany died, in 1115, and the following year the city obtained many judicial and economic concessions from Henry V. Bologna joined the Lombard League against Frederick Barbarossa in 1164 which ended with the Peace of Costanza in 1183; after which, the city began to expand rapidly (this is the period in which its famous towers were built) and it became one of the main commercial trade centres thanks to a system of canals that allowed large ships to come and go.
Giovanni's reign ended in 1506 when the Papal troops of Julius II besieged Bologna and sacked the artistic treasures of his palace. From that point on, until the 18th century, Bologna was part of the Papal States, ruled by a cardinal legato and by a Senate which every two months elected a gonfaloniere (judge), assisted by eight elder consuls. In 1530, in front of Saint Petronio Church, Charles V was crowned Holy Roman Emperor by Pope Clement VII.
The period of Papal rule saw the construction of many churches and other religious establishments, and the reincarnation of older ones. At this time, Bologna had ninety-six convents, more than any other Italian city. Artists working during this period in Bologna established the Bolognese School which includes Annibale Carracci, Domenichino, Guercino and others of European fame.
Bologna was bombed heavily during World War II. The strategic importance of the city as industrial and railway hub connecting northern and central Italy made it a strategic target for the Allied forces. On July 16, 1943 a massive aerial bombardment destroyed much of the historic city centre and killed scores of people. The main railway station and adjoining areas were severely hit, and 44% of the buildings in the centre were listed as having been destroyed or severely damaged. The city was heavily bombed again on September 25. The raids, which this time were not confined to the city centre, left 936 people dead and thousands injured.
After World War II, Bologna became a thriving industrial centre as well as a political stronghold of the Italian Communist Party, leading the Italian political "Red Quadrilateral".
- Bologna Cathedral dedicated to Saint Peter, is the seat and the metropolitan cathedral of the Archbishop of Bologna. There was already a cathedral on the site (on the present Via Indipendenza) in 1028, accompanied by a pre-Romanesque campanile with a circular base (in the architectural tradition of Ravenna). This church was destroyed by a devastating fire in 1141. It was reconstructed, and consecrated by Pope Lucius III in 1184. In 1396 a high portico (protiro) was added to the west front, which was rebuilt in 1467. In 1582 Pope Gregory XIII elevated the Bishop of Bologna to Archbishop, and accordingly the cathedral was elevated to the rank of "metropolitan church" (a bishop's seat with jurisdiction over other bishops and dioceses in its territory). By order of Cardinal Gabriele Paleotti a radical remodelling of the interior of the building began in 1575, of which the crypt and the Greater Chapel (Capella Maggiore) survive. The alterations were so extensive however as to cause the vaults to collapse in 1599, and the decision was then made to rebuild the main part of the cathedral from scratch. Work on the new building started in 1605. A new façade was added between 1743 and 1747, to designs by the architect Alfonso Torreggiani, on the instructions of Pope Benedict XIV.
- The Towers of Bologna are a group of medieval structures in Bologna. The two most prominent ones, also called the Two Towers, are the landmark of the city. The Two Towers, both of them leaning, are the symbol of the city. They are located at the intersection of the roads that lead to the five gates of the old ring wall (mura dei torresotti). The taller one is called the Asinelli while the smaller but more leaning tower is called the Garisenda. Their names derive from the families which are traditionally credited for their construction between 1109 and 1119. However, the scarcity of documents from this early period makes this in reality rather uncertain. The name of the Asinelli family, for example, is documented for the first time actually only in 1185, almost 70 years after the presumed construction of the tower which is attributed to them.
- The Palazzo del Podestà is a civic building in Bologna. The edifice was built around 1200 as the seat of the local podestà, the various functionaries of the commune. It stands on the Piazza Maggiore, near the Palazzo Communale and facing the Basilica of St. Petronio. Proving insufficient for the massive participation of the people in the city's government, it was in 1245 flanked by the Palazzo Re Enzo, over which stands the Torre dell'Arengo, whose bell was used to call the people during emergencies.The Palazzo del Podestà is a long building, with a large hall on the upper floor. The lower floor is a double open arcade, the so-called Voltone del Podestà, through which pass two lanes of shops.
- International Museum and Library of Music. The Civico Museo Bibliografico Musicale, founded in 1959 to hold the Comune di Bologna’s collection of musical objects, was renamed International Museum and Library of Music in 2004 with the opening of the museum’s site, the Palazzo Sanguinetti, in the historic center of Bologna. The building was reopened to the public after a long and careful restoration that brought the rich, interior frescoes back to their original splendor. These frescoes were completed between the end of the 18th century and the beginning of the 19th century, and provide one of the greatest examples of the Napoleonic and Neoclassical period in Bologna.
- The Sanctuary of the Madonna of San Luca is a basilica church sited atop Colle or Monte della Guardia, in a forested hill some 300 metres above the plain, just south-west of the historical centre of the city. While a road now leads up to the sanctuary, it is also possible to reach it along a (3.5 km) monumental roofed arcade (Portico di San Luca) consisting of 666 arches, which was built in 1674-1793. It was meant to protect the icon as it was paraded up the hill. A yearly procession from the Cathedral of San Pietro in the centre of Bologna to the Sanctuary goes along this path. Originally the arches held icons or chapels erected by the patron family. The Sanctuary was meant to house a miraculous icon of the virgin. A church or chapel existed on the hill for about a thousand years. The present church was constructed in 1723 using the designs of Carlo Francesco Dotti.