The city of Regensburg was already a settlement in prehistoric times. In 179 the Roman Emperor Marcus Aurelius built the fortification of Castra Regina. St. Boniface founded in 739 the bishopric of Regensburg. Regensburg was an important trade center and became a Free Imperial city in 1245. From 1663 until 1806 the city was the seat of the Reichstag of the Holy Roman Empire. In 1810 Regensburg became part of the Kingdom of Bavaria.