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.
Donausteig (Danube Trail)
Among the points of interest along the trail are the "Strudengau" with the "Stillensteinklamm", the "Wolfschlucht" near Bad Kreuzen, the Floodplains of the Northern Machland, the "Klamschlucht", the "Pesenbachtal", the "Obere Donautal Oberösterreichs" with the "Schlögener Schlinge", the "Rannatal" and the "Tal des Kleinen Kößlbachs".The "Donausteig" trail runs along the Danube River, starting in Passau and passing through Linz, the former European Capital of Culture, to Grein, an Upper Austrian town with an altitude of 218 meters above sea level, the lowest in the region.