Danube
The Danube was once a long-standing frontier of the Roman Empire, and today flows through 10 countries, more than any other river in the world. Originating in Germany, the Danube flows southeast for , passing through or bordering Austria, Slovakia, Hungary, Croatia, Serbia, Romania, Bulgaria, Moldova and Ukraine before draining into the Black Sea. Its drainage basin extends into nine more countries. The Danube river basin is home to fish species such as pike, zander, huchen, Wels catfish, burbot and tench. It is also home to a large diversity of carp and sturgeon, as well as salmon and trout. A few species of euryhaline fish, such as European seabass, mullet, and eel, inhabit the Danube delta and the lower portion of the river.
Lower Danube Circle
The Lower Danube Circle or Under Danube Circle () was one of the administrative districts (German: "Bezirke" or "Regierungsbezirke") of the Kingdom of Bavaria between 1806 and 1837. It was named after its main river, the Danube and was the predecessor of the administrative district of Lower Bavaria ("Regierungsbezirk Niederbayern"). Its administrative headquarters were in Passau, but the appelate court was in Straubing.The district was divided in the following judicial districts ("Landgerichte"), according to the original borders of the districts of the former territories ("Herrschaftsgerichte"):