The Iskar is a right tributary of the Danube. With a length of 368 km, it is the longest river that runs entirely within Bulgaria. Originating as three forks in Balkan's highest mountain range Rila, the Iskar flows in a northern direction until its confluence with the Danube. As it flows northwards it fuels the largest artificial lake in the country, the Iskar Reservoir, forms the divide between the Vitosha and Plana Mountains in the west and the Sredna Gora mountain range in the east before entering the Sofia Valley, which contains the nation's capital Sofia. From there the Iskar runs through the Balkan Mountains, forming the spectacular 84 km long Iskar Gorge. As it crosses the mountains, its water course turns in a north-eastern direction at Lakatnik. North of the Balkan Mountains, the river crosses the Danubian Plain and finally flows into the Danube between the villages of Baykal and Gigen. Geologically, Iskar is the oldest river in the Balkan Peninsula.
Iskar near Karlukovo
One of the glacial Musala Lakes in the Rila mountains that feeds the uppermost tributaries of the Iskar
Panoramic view of the Iskar Gorge
The Iskar near German
The Danube is the second-longest river in Europe, after the Volga in Russia. It flows through Central and Southeastern Europe, from the Black Forest south into the Black Sea. A large and historically important river, it was once a frontier of the Roman Empire. In the 21st century, it connects ten European countries, running through their territories or marking a border. Originating in Germany, the Danube flows southeast for 2,850 km (1,770 mi), passing through or bordering Austria, Slovakia, Hungary, Croatia, Serbia, Romania, Bulgaria, Moldova, and Ukraine. Among the many cities on the river are four national capitals: Vienna, Bratislava, Budapest, and Belgrade. Its drainage basin amounts to 817,000 km² and extends into nine more countries.
The Danube in Budapest
The hydrogeographical source of the Danube at St. Martin's Chapel in Furtwangen im Schwarzwald: the Bregquelle, the source of the Danube's longest headstream, the Breg, where the Danube is symbolized by the Roman allegory for the river, Danuvius.
The symbolical source of the Danube in Donaueschingen: the source of the Donaubach (Danube Brook), which flows into the Brigach.
The Tisza is the longest tributary of the Danube.