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.
Ulm
Ulm lies at the point where the rivers Blau and Iller join the Danube, at an altitude of above sea level. Most parts of the city, including the old town, are situated on the left bank of the Danube; only the districts of Wiblingen, Gögglingen, Donaustetten and Unterweiler lie on the right bank. Across from the old town, on the other side of the river, lies the twin city of Neu-Ulm in the state of Bavaria, smaller than Ulm and, until 1810, a part of it (population c. 50,000).