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The Danube Sinkhole ((ドイツ語:Donauversinkung) or ドイツ語:''Donauversickerung'') is an incipient underground stream capture in the Upper Danube Nature Park. Between Immendingen and Möhringen and also near Fridingen (Tuttlingen), the water of the Danube sinks into the riverbed in various places. The main sinkhole is next to a field named ''Brühl'' between Immendingen and Möhringen. The term “sinking” is more accurate then “seeping”, because, instead of just distributing into the soil, the Danube’s water flows through underground caverns to the Aachtopf, where it emerges as the river Radolfzeller Aach. == Hydrography == The sinking Danube water disappears into a karst water system of the ''well-stratified limestone formation'' (the ''ox2'' layer) of the White Jura and appears again in a horizontal limestone layer (the ''ki4'' layer), approximately twelve kilometers away at Aachtopf.〔H. Binder: ''Höhlenführer Schwäbische Alb'', H. Jantschke 7th ed, 2003; p. 260〕 It then flows as Radolfzeller Aach into Lake Constance at Radolfzell. Thus, a part of the Danube water also flows into the Rhine. This geographical situation is a striking feature of the large European Watershed, which separates the catchment areas of the North Sea and the Black Sea. The water flows out through a variety of small to very small cracks and crevices; the karst in these places is apparently at an early stage of development. The cave system of Aachtopf, that is the underground river Danube is, however, probably already well developed. They can be inferred from the tight correlation in water temperatures of the Danube and Aachtopf spring which matches the behaviour of an underground river better than a branching system. In the 1960s, Jochen Hasenmayer discovered and explored the first 400 meters of a large clam-shaped hole called the ''Aachhöhle''. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Danube Sinkhole」の詳細全文を読む スポンサード リンク
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