River Danube does not flow through which one of the following capital cities in Europe?

The Danube is Europe's second-longest river and flows through four capital cities: Vienna (Austria), Bratislava (Slovakia), Budapest (Hungary) and Belgrade (Serbia). Prague, the capital of the Czech Republic, lies on the Vltava River, which is a tributary of the Elbe — NOT on the Danube. Therefore, Prague is the correct answer.