Source of the Danube
As early as 1847 the following definition can already be found in the "Universallexikon des Großherzogtums Baden" (Universal Lexicon of the Grand Duchy of Baden): “Danube, the biggest river of Germany, rises at the Martinskapelle in a wild and lonely area of the Black Forest, is called Brege at its origin and forms the river Danube in Donaueschingen where it is unified with the Brigach." (German original: „Donau, der größte Fluß Deutschlands, entspringt bei der Martinskapelle in einer wilden und einsamen Gegend des Schwarzwaldes, heißt am Anfang Brege… und bildet erst in Donaueschingen, wo sie sich mit der Brigach vereinigt, die Donau.“)
Hydrology of Hungary
The primaeval Danube first silted up the basin of the Pannonian Sea which now forms the Eastern Slovak Lowland on the left bank of the river and the Little Hungarian Plain on the right bank. It flowed towards the south into Transdanubia and then followed the present-day course of the Drava into an interior lake system in the south of the present Great Plain. Later the Danube was diverted to the east by tectonic uplift, finding an outlet through the Visegrád gap. During the Quaternary the Great Plain continued to sink, meanwhile the Börzsöny and the Visegrád mountains were rising. The result was the gorge, or a deep terraced valley cut through the mountains by the Danube at what is now the Danube Bend at Visegrád, between Esztergom and Vác. Once through the gorge, the Danube fanned out into the Great Hungarian Plain, depositing alluvial cones. The present north-south course was formed by the river in the late Pleistocene.