Danube
The Danube flows through many cities, including four national capitals (shown below in bold), more than any other river in the world. Ordered from the source to the mouth they are:
The Danube is navigable by ocean ships from the Black Sea to Brăila in Romania and by river ships to Kelheim, Bavaria, Germany; smaller craft can navigate further upstream to Ulm, Württemberg, Germany. About 60 of its tributaries are also navigable.
Geography of Hungary
The major rivers in the country are the Danube and Tisza. The Danube is navigable within Hungary for 418 kilometers. The Tisza River is navigable for 444 km in the country. Less important rivers include the Drava along the Croatian border, the Rába, the Szamos, the Sió, and the Ipoly along the Slovakian border. Hungary has three major lakes. Lake Balaton, the largest, is 78 km long and from 3 to 14 km wide, with an area of 600 square km . Hungarians often refer to it as the "Hungarian Sea". It is Central Europe's largest freshwater lake and an important recreation area. Its shallow waters offer good summer swimming, and in winter its frozen surface provides excellent opportunities for winter sports. Smaller bodies of water are Lake Velence (26 square km) in Fejér County and Lake Fertő (Neusiedler See—about 82 square km within Hungary), and the artificial Lake Tisza.