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.
Source of the Danube
For centuries, the two cities Furtwangen and Donaueschingen competed for an official status which declares their own source as the official source of the Danube. The city Furtwangen is located along the upper river Breg, while the city Donaueschingen is located at the symbolic source of the Danube. At times, the issue even involves the government of Baden-Württemberg. After the city council Donaueschingen intervened in 1981, for example, the Ministry of the Interior in Stuttgart announced that "the source of the Breg is not anymore displayed as the source of the Danube on ministerial maps. The land surveying office was instructed to act accordingly." However, the former minister for agriculture and forestry confirmed in a document addressed to Prof. Öhrlein in 1982: "Getting back to the issue regarding the source of the Danube, I can once again confirm that the so-called source of the Danube in Donaueschingen is certainly not the real source of the river Danube, if analysed with geographical and hydrological criteria. The river Breg can rightly be called the main stream of the Danube."