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Ice cave. View of the interior of an ice cave. This cave is part of the Schellenberger Eishohle caves in the Alps around Marktschellenberg, southern Germany. Such caves are typically formed by water erosion. The caves are kept icy by winds. In winter, a cold wind blows through the caves, freezing the water formed by melting snow and ice in summer. In summer, a cold breeze blows from the cave depths to the entrance, preventing melting. (KEYSTONE/SCIENCE PHOTO LIBRARY/BERNHARD EDMAIER)