Pingtang county, Guizhou province is the most developed karst area in Southwest China, as it contains the most karst tiankengs (an area of naturally formed pits) of any region in the world. In an area of just 20 square kilometers surrounding Longfeng Mountain, there are 12 tiankengs of various sizes, some with a depth of more than 300 meters. The highest altitude in the area is 1,137 meters, while the lowest is 548 meters. They center around Dadaihe, forming a magnificent natural wonder.