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.
Danube Valley Railway (Baden-Württemberg)
The Danube Valley Railway runs alongside the Danube river and crosses it several times. From Immendingen the line runs across the Upper Danube Nature Park "(Naturpark Obere Donau)", brushing up against the southern edge of the Schwäbische Alb, all the while following the course of the Danube. Between the towns of Inzigkofen and Herbertingen, the Danube Valley Railway again shares its tracks, this time with the Zollernalb Railway. At Ehingen (Donau), the line leaves what is known as the Danube valley today, and follows the valley formed by the Danube in times past, along the rivers Schmiech, Ach, and Blau. The railway again touches the border of the Schwäbische Alb between Allmendingen and Blaustein, and meets its eponymous river again at the line's terminus in Ulm.