The Blauhohle is the largest cave system in the Swabian Alps in southern Germany. The Blauhohle presumably originated in a time when the Danube still flowed through the Blau valley. Since the shifting of the Danube several small rivers the Schmiech the Ach and the Blau have flowed through this valley. The cave system begins about 21 meters under water at the base of the Blautopf. Given a list of categories: company, educational institution, artist, athlete, office holder, mean of transportation, building, natural place, village, animal, plant, album, film or written work, what category does the paragraph belong to?
A:
Natural Place