Reggio Emilia is a city in northern Italy, in the Emilia-Romagna region. It has about 170,000 inhabitants and is the comune of the Province of Reggio Emilia. The town is referred to by its more official name of Reggio nellEmilia listen. The inhabitants of Reggio nellEmilia usually call their town by the name of Reggio. In some ancient maps the town is named Reggio di Lombardia, the old town has an hexagonal form, which derives from the ancient walls, and the main buildings are from the 16th–17th centuries. The comunes territory is totally on a plain, crossed by the Crostolo stream, Reggio began as a historical site with the construction by Marcus Aemilius Lepidus of the Via Aemilia, leading from Piacenza to Rimini. Reggio became an administration centre, with a forum called at first Regium Lepidi, simply Regium. During the Roman age Regium is cited only by Festus and Cicero, however, it was a flourishing city, a Municipium with its own statutes and art collegia. Apollinaris of Ravenna brought Christianity in the 1st century CE, the sources confirm the presence of a bishopric in Reggio after the Edict of Milan.
In 440 the Reggio diocese was placed under the jurisdiction of Ravenna by Western Roman Emperor Valentinianus III, at the end of the 4th century, Reggio had decayed so much that Saint Ambrose included it among the dilapidated cities. Further damage occurred with the Barbarian invasions, after the deposition of Romulus Augustulus in 476 Reggio was part of Odoacers realm. In 489 it came under Ostrogothic control, from 539 it was part of the Roman Empire, Reggio was chosen as Duchy of Reggio seat. In 773 the Franks took Reggio, charlemagne gave the bishop the authority to exercise royal authority over the city and established the diocese limits. In 888 Reggio was handed over to the Kings of Italy, in 899 the Magyars heavily damaged it, killing Bishop Azzo II. As a result of new walls were built. On 31 October 900 Emperor Louis III gave authority for the erection of a castrum in the citys centre. In 1002 Reggios territory, together with that of Parma, Modena and Ferrara, were merged into the March of Tuscany, Reggio became a free commune around the end of the 11th or the beginning of the 12th century.
In 1167 it was a member of the Lombard League and took part in the Battle of Legnano, in 1183 the city signed the Treaty of Konstanz, from which the citys consul, Rolando della Carità, received the imperial investiture