Regensburg is a city in eastern Bavaria, at the confluence of the Danube, Naab and Regen rivers. It is capital of the Upper Palatinate subregion of the state in the south of Germany. With more than 150,000 inhabitants, Regensburg is the fourth-largest city in the State of Bavaria after Munich, Nuremberg and Augsburg. From its foundation as an imperial Roman river fort, the city has been the political, economic and cultural center of the surrounding region; it is still known in the Romance languages by a cognate of its Latin name of "Ratisbona". Later, under the rule of the Holy Roman Empire, it housed the Perpetual Diet of Regensburg.
The medieval centre of the city is a UNESCO World Heritage Site. In 2014, Regensburg was among the top sights and travel attractions in Germany.