The Blautopf 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.
One characteristic of a Karst environment is that water, which drains quickly through the limestone in one area, surfaces in another. Karst environments only have subterranean drainage, and there are no bodies of water above ground.
Therefore, the size of the Blautopf depends greatly on the level of rainfall, though it never entirely dries out. The Blautopf is the second largest spring in Germany, after the Aachtopf.