The inconspicuous Grundlose Kuhle is a circular hole with a small pond in its center. In contrast to the surrounding heathland, the Kuhle is not a glacial geological formation. Rather, various sediments were washed out by acid precipitation. Interestingly, the pond maintains its water level, although it has neither inflows nor outflows. In fact, the Kuhle is not groundless, but at least five meters deep.
About 1100 meters southeast of Ahlften is the so-called Grundlose Kuhle. A circular crater about 40 m in diameter, with an almost circular small pond about 5 m deep and 20 m in diameter. The water level is 1 ½ m above the nearby Böhme. Although it has neither an inflow nor an outflow, it hardly changes. The sinkhole was caused by salt leaching in the soil and represents a geological karst formation of national importance. [5] There are many legends about the Grundlose Kuhle. One says that there was a castle on this spot in ancient times.