With an average water flow of around 6855 m³/s[3] and a total length of 2857 kilometers[1], the Danube is the second largest and second longest river in Europe after the Volga. The river drains large parts of central and south-eastern Europe. It flows through or touches ten countries (Germany, Austria, Slovakia, Hungary, Croatia, Serbia, Bulgaria, Romania, Republic of Moldova and Ukraine) - more than any other river on earth.
The Danube takes its name from the union of two source rivers, the Brigach and the larger Breg, both of which have their source in the central Black Forest. It crosses three large basin landscapes: the northern foothills of the Alps and the Vienna Basin (upper reaches), the Pannonian lowlands (middle reaches) and the Wallachian lowlands (lower reaches). It cuts through the separating mountains in narrow valleys, the best-known sections of which are the Danube Gorge near Beuron, the Danube Gorge near Weltenburg, the Wachau, the Hainburg Gate (also Pressburg Gate) and the Iron Gate. The river flows into the Black Sea via the extensive Danube Delta.
The Danube is one of the oldest and most important European trade routes and connects different cultures. Political tensions and wars repeatedly caused the waterway to be closed and obstructed. Since the fall of the Iron Curtain, the Danube has regained its economic importance. The river connects many species-rich and unspoiled natural areas and is an important location for hydroelectric power plants.