The Blautopf is probably the most famous karst spring in the Swabian Alb. Its incomparable turquoise-blue colour has inspired poets for centuries. Since the exploration of the Blauhöhlen cave system, the natural wonder has also gained international fame. After having passed a small funnel-shaped entrance at the bottom of the 21-metre-deep Blautopf, cave divers entered huge, dry halls of breathtaking beauty. The Blauhöhlen cave system has been explored over a length of more than 13 kilometers by now.
At the Blautopf, precipitation water from an area of more than 160 square kilometres comes to the surface. The discharge of the spring, i.e. the amount of water that emerges, varies depending on the amount of precipitation. When the discharge is high, the water appears to "boil" as it flows out under high pressure. At low discharge, the water is crystal clear and bright blue. It feeds the river Blau, which flows into the Danube at Ulm.
The Blautopf and the Blaubeurer Alb are designated as "National Geosites".