Current data indicate that the recorded 79 karst caves in namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />China are longer than 5 km and 62 deeper than 250 m. 24 cave chambers with individual floor areas are larger than 20 000 m2, and 23 separate underground river systems longer than 50 km. Most of these caves and cave river systems are in southwestern China, where massive, thick and continuous sequences of carbonate rock are outcrop with the area about 500 000 km2. Warm and moist, subtropical monsoon climate contributes to the development of large karst caves.