The Danube (German, Donau; Slovakian, Dunaj; Hungarian, Duna; Romanian Dunărea; Serbo-Croatian Dunav; Ukrainian, Äóíàé) is the longest river in Europe and the only big river flowing eastwards. It originates in the Black Forest in Germany as two smaller rivers—the Brigach and the Berg—which join at Donaueschingen and it is from here that it is known as the Danube. It flows in south-eastern direction for a distance of 2859 km and empties into the Black Sea via the Danube Delta (bordering on the Ukraine) in Romania. The deepest areas of the river reach more than 30 m in depth.
The Danube’s riverbed is the largest swampy area in Europe. There are more reeds here than anywhere else in the world. The river holds yet another world record – it is the home of more than 78% of the Europe’s bird population.
The Danube flows through nine countries, namely Germany, Austria, Slovakia, Hungary, Croatia, Serbia, Bulgaria, Romania and Ukraine. The population of cities situated on the river is 83 million people in total.
In the third century AD the river constitutes the northern border of the Roman Empire and the fortresses built along its banks aimed to protect locals from the attacks of the Goths, the Huns and Slavic tribes. Later the Danube served as a waterway providing access to the city of Constantinople. Crusaders also use it as a waterway in their military expeditions to the Holy Land. During the Middle Ages the river facilitates the Turkish invasion into Western and Central Europe. In the eighteenth century the Danube starts being used as a commercial route. Maria Theresa, Queen of Hungary, who succeeded to the Habsburg monarchy, establishes a unit which is to regulate navigation on the river. In 1830 the first commercial ship sailed from Vienna to Budapest.