Die Blaue Donau.
The Blue Danube.
Absolutely not recommended to swim in the Danube.
Not only that the water is dirty,
but the streams are really strong.
Looks somehow tempting in this angle though.
The Danube originates in Black Forest In Germany,
flows 2.872km passing through
Vienna, Bratislava, Budapest and Belgrade
before emptying into the Black Sea.