The Blautopf (German for Blue Pot; "blau" means blue, "topf" means pot) is a spring that serves as the source of the river Blau in the karst landscape on the Swabian Jura's southern edge, in Southern Germany. It is located in the city of Blaubeuren, approximately 16 km (9.9 mi) west of Ulm. It forms the drain for the Blau cave system and feeds the river Blau, which after 14.5 km (9.0 mi), flows into the river Danube in the city of Ulm. Because of its high water pressure, the spring has developed a funnel-like shape, which at its deepest point has a depth of 21 metres (69 ft).