The Congo Caves are located in Precambrian limestones at the foothills of the Swartberg range near the town of Oudtshoorn, in the Western Cape Province of South Africa. The principal cave is one of the country's finest, best known, and most popular tourist caves, and attracts many visitors from overseas. Although the extensive system of tunnels and chambers go on for over four kilometres, only about a quarter of this is open to visitors, who may proceed into the cave only in groups supervised by a guide. Tours are conducted at regular intervals on most days—there is a "Standard Tour" which takes an hour and an "Adventure Tour" which takes an hour and a half. The "Adventure Tour" consists of crawling through narrow passages and climbing up steep rock formations guided by small lights. The caves contain halls and limestone formations (on both tours) as well as small passages on the Adventure Tour. The smallest passage that tourists will have to pass through on the Adventure Tour is just under 15 cm to exit.