world over 1,000km in length, and many thousands of rivers in total. The longest in Europe is the Volga, in Russia, while the Danube runs through the most capital cities with four; Vienna, Bratislava, Budapest and Belgrade. The most popular rivers in the world for river cruises are the Danube, Rhine, Seine and Volga in Europe, the Yangtze in China, the Nile in Africa, the Amazon in South America and the Mississippi in the US. However there are many others visited by major river cruise lines.