List of tributaries of the Danube
The Danube is Europe's second-longest river. It starts in the Black Forest in Germany as two smaller rivers—the Brigach and the Breg—which join at Donaueschingen, and it is from here that it is known as the Danube, flowing generally eastwards for a distance of some , passing through several Central and Eastern European capitals, before emptying into the Black Sea via the Danube Delta in Romania.
Hydrology of Hungary
The Danube is the second longest river in Europe, after the Volga. Its upper flow is outside of Hungary, but its middle section starts at Devín, close to the Hungarian border. This section of the river stretches until the Iron Gate, between Serbia and Romania. The lower section of the river crosses the Romanian Plain and flows into the Black Sea through a delta. The Hungarian section of the river is long, from which forms the border between Hungary and Slovakia, from Rusovce to the mouth of the Ipeľ ().