No river flows through Vienna, Belgrade and Portugal. The Danube does flow through Vienna and Belgrade, but not through Portugal.
River Danube flows through Vienna,Budapest and Belgrade
The Danube flows through Belgrade, and the Sava joins it there.
Danube
The Sava River
The answer you are looking for is the Danube. It actually flows through 4 capital cities: Vienna - Austria Budapest - Hungary Belgrade - Serbia Bratislava - Slovakia
The Danube flows through four capitals: Bratislava, Belgrade, Budapest, and Vienna.
The Danube runs through Belgrade.
The river that flows through Vienna, Budapest and Belgrade is THE Danube river, who happens to cross Germany, Slovakia, Austria, Hungary, Croatia, Serbia, Romania borders of Bulgaria and joins the Black Sea at the borders of Romania and Ukraine.
It flows in Europe through Austria (Vienna), Hungary (Budapest), Serbia (Belgrade), Slovakia (Bratislava) & Romania and then into the Black Sea.
This river is Danube.
The river that flows through Rome should be River Tiber.