The “Seegrotte” near Hinterbrühl in Lower Austria, about 30 kilometers away from Vienna, is an underground cave system. In fact it is the largest subterranean lake in Europe. Today visitors…
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The “Seegrotte” near Hinterbrühl in Lower Austria, about 30 kilometers away from Vienna, is an underground cave system. In fact it is the largest subterranean lake in Europe. Today visitors…