The Danube River is the second longest river in Europe, rising in Germany and flowing through 10 countries before emptying into the Black Sea. For hundreds of years it has served as an important trade route and transportation artery for the nations along its banks. Today the Danube remains a vital transportation route and source of hydroelectric power, with cities like Vienna, Budapest, and Belgrade relying on the river economically. Maintaining the river's role in both transportation and protecting its biodiversity remains important for the countries it flows through.