The Danube is the second longest river in Europe after the Volga. It is the only large river 
in Europe that flows from west to east and flows into the Black Sea.
In addition, the Danube is the river that flows through the most countries in the world 
– 10 in number (Germany, Austria, Slovakia, Hungary, Croatia, Serbia, Bulgaria, Romania, Moldova and Ukraine.), and its catchment basin is extends, in addition to the territories of the above 10 countries, to the territories of another 9 countries (Switzerland, Italy, the Czech Republic, Poland, Slovenia, Bosnia and Herzegovina, Montenegro, Albania and Kosovo). Length 2852 km. Catchment area 817,000 km².