Hundreds of rivers and their tributaries cross the European continent. Here we highlight those over 600 miles in length, and a few others of note. DANUBE Beginning in the Black Forest region of Germany, it flows across central Europe and the countries of Austria, Hungary, Croatia and Yugoslavia. It then forms the border between Romania and Bulgaria, turning north across Romania to eventually end in the Black Sea.

It's (1,771 miles) (2,850 km) in length, and one of the most significant commercial waterways on the continent.

The Danube is one of the most important rivers in Europe. It is the second longest river in Europe only the Volga is longer. The Danube passes through many countries which include Romania, Bulgaria, Croatia, Yugoslavia, Hungary, Slovakia, Austria and Germany. It is increasingly becoming a link between these European countries.

The Danube is of International importance as it is the only river in Europe that flows east. However, until 1950 it was not able to be navigated during it's passage through the Transylvanian Alps. Also, the Danube passes through several conflicting countries, which provides many problems in settling the laws of the region.Today there is hope that the Danube river will allow Eastern Europe to become more connected to the rest of Europe.

DNIEPER Rising in the southwestern part of the Russian Federation, it flows generally south through Belarus, then southeast through Ukraine, ending in the Black Sea. Overall it's (1,420 miles) (2,285 km) in length.

The Dnieper was known to both the Ancient Greeks and the Romans. In the Middle Ages, it was an important trade route between the Baltic Sea and Byzantium and the Black Sea. Kiev, the capital of early medieval Rus', was located on the Dnieper. Most of the other important medieval Rus' towns such as Chernihiv, Pereiaslav and Smolensk, were also either on the Dnieper or one of its tributaries.

ELBE Rising in the Czech Republic, the Elbe River then flows north through Germany, ending in the North Sea near Cuxhaven. It's (724 miles) (1,165 km) in length.

It begins in the Sudeten Mountains of the Czech Republic and flows some 725 miles (1,165 km) to the North Sea through the Czech Republic and Germany. Tributaries include the Vltava in the Czech Republic and the Mulde, Saale, and Havel in Germany.

The lower 60 miles (95 km) of the Elbe form a broad estuary navigable by oceangoing ships. The western end of the Kiel Canal enters the estuary at Brunsbüttelkoog. The German portion of the river has long been an important inland waterway.

The largest cities on the river are Hamburg and Dresden, Germany.

PO Italy's longest river begins in the upper reaches of the Alps, flowing west to east across northern Italy, ending in the Adriatic Sea. It's (405 miles) (652 km) in length. The Po forms the boundary between the regions of Lombardy and Emilia-Romagna (south) and Veneto (north). It receives the waters of the Dora Riparia and the Dora Baltea below Turin; other principal tributaries are the Sesia, Ticino, Adda, Oglio, and Mincio from the north. Among the many streams that drain into the Po from the south, the Tanaro (from the Maritime Alps) and the Scrivia and Trebbia (from the Apennines) are important; but many of the others are rain-fed and torrential and carry little water through much of the year. Throughout its middle and lower courses the Po describes many meanders, which have left oxbows (circular lakes).

RHINE Forming in the mountains of southeastern Switzerland, this legendary river flows west, forming Switzerland's northeastern border with Germany, then runs directly north through western Germany forming part of that country's border with France, then finally dissecting the Netherlands and ending in the North Sea.

Numerous tributaries and branches run in all directions and in overall length is (820 miles) (1,319 km).

It has also served as a defensive feature and has been the basis for regional and international borders. The many castles and prehistoric fortifications along the Rhine testify to its importance as a waterway. River traffic could be stopped at these locations, usually for the purpose of collecting tolls, by the state that controlled that portion of the river.

RHONE Begin high in the Swiss Alps, this fast moving river flows into the eastern end of Lake Geneva, then south through south-eastern France, emptying into the Mediterranean Sea.

Small branches run in all directions, and in overall length, it's (300 miles) (485 km).

The valley of the Rhône, in both Switzerland and France, is a primary transportation route followed by major railways and roads. The Rhône-Saône valley in France has been a corridor between the Mediterranean and northern Europe since ancient times.

As an inland waterway the Rhône is of limited importance, partly because its delta is unnavigable. Traffic consists mainly of freight barges in the section between Lyon and Aries, at the head of the delta. A canal links Arles with the nearby port of Marseille. There is also shipping north of Lyon on the Saône. Numerous dams on the Rhône and its tributaries, especially in the Alps, provide abundant hydroelectric power.