The city is the political, economic and cultural centre of Eastern Bavaria and the capital of the Bavarian administrative region Upper Palatinate.The medieval centre of the city is a UNESCO World Heritage Site and a testimony of the city's status as cultural centre of southern Germany in the Middle Ages.In 792, Regensburg hosted the ecclesiastical section of Charlemagne's General Assembly, the bishops in council who condemned the heresy of adoptionism taught by their Spanish counterparts, Elipandus of Toledo and Felix of Urgel.After the partition of the Carolingian Empire in 843, the city became the seat of the Eastern Frankish ruler, Louis II the German.The Celtic name Radasbona was the oldest given to a settlement near the present city. In 179, a new Roman fort Castra Regina ("fortress by the river Regen") was built for Legio III Italica during the reign of Emperor Marcus Aurelius.It was an important camp on the most northerly point of the Danube: it corresponds to what is today the core of Regensburg's Old City or Altstadt east of the Obere and Untere Bachgasse and West of the Schwanenplatz.In 2014, Regensburg was among the top sights and travel attractions in Germany.
With over 140,000 inhabitants, Regensburg is the fourth-largest city in the State of Bavaria after Munich, Nuremberg and Augsburg.
From about 530 to the first half of the 13th century, it was the capital of Bavaria.
Regensburg remained an important city during the reign of Charlemagne.
It is believed that as early as in late Roman times the city was the seat of a bishop, and St Boniface re-established the Bishopric of Regensburg in 739.
From the early 6th century, Regensburg was the seat of a ruling family known as the Agilolfings.