Cottbus is a university city and the second-largest city in the German state of Brandenburg after the state capital of Potsdam. With around 100,000 inhabitants, it is the most populous city in Lusatia, and since December 2023, it is the easternmost German city with a population surpassing 100,000. Cottbus lies in the Sorbian settlement area of Lower Lusatia, and is the second-largest city on the River Spree after Berlin, which is situated around 125 km (78 mi) upstream. The city is located on the shores of Germany's largest artificial lake, the Cottbuser Ostsee.