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.
Ybbs
Its source is located on the Zellerrain Pass near Mariazell. The river is called the "Weiße Ois" in the beginning, then onwards from the border between Lower Austria and Styria to Lunz am See it is called the "Ois", and from there until it meets the Danube at "Ybbs an der Donau", it is called "the Ybbs".