Limestone deposits of Paleozoic age are quite common in Korea, and a number of spectacular karst areas with caves can be found on the peninsula. North Korea is said to have 11,000 caves. Because of the hot and wet climate the caves are often rather big. They are used by the locals for various purposes and for a very long time. There are archaeological remains, cave temples and caves used for modern purposes. Because of the long-lasting conflict with South Korea and the western world, several caves were used for military purposes. However, this has not really been proven and is not relevant for tourists, as it is not possible to visit this places.
It is still difficult to visit this country, and both the development of tourism and the information about it is in a poor state. We know of two caves which were opened to foreign tourists during the last years under growing economic pressure. It seems there are other sites which are only open to locals.
T'ongnyonggul is one of the most famous caves of the country. It is located near Yongbyon on the southern side of the Ch'ongchongang River. It is about 5 km long and has several chambers which are about 150 m wide and 50m high. Although it is mentioned various times, we could not find detailed info, probably because of a wrong transkription of the name. The closeness to the nuclear plant at Yongbyon and the frequent rumours about underground factories and power plants suggest, that various caves in the area were equipped for military purposes.