The Kelle is a gypsum cave near Appenrode and is located in the fascinating karst landscape of the Südharz Nature Park. As the northernmost of the eight National Natural Landscapes in Thuringia, the Southern Harz Nature Park impresses with its diversity of landscapes. Here, the southern mountain ranges of the Harz Mountains meet a belt of limestone, creating the striking karst landscape. The water-soluble gypsum rock has created natural spectacles such as sinkhole lakes, sinkholes, winding streams, karst springs, steep gypsum slopes and gypsum caves such as the Kelle. Originally, the Kelle was a giant hall approx. 85 m long and filled with water. Over time, however, it was leached out and reshaped by stagnant karst water, so that today it only consists of a large sinkhole and a half-open grotto with a small lake.