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
The spring of the river Breg is situated in the north of Furtwangen next to the St. Martin's Church near the Kolmenhof (restaurant). The Breg is for geographical and hydrological reasons longer and has a bigger water flow than the Brigach which is why its spring is the main origin of the upper Danube. The dominance of the Breg is established by the following data: