THE CAVE  | Arnhem Cave is still in a completely natural state. It developed through the solution of limestone and dolomite from between thin layers of quartzite and shale. The insoluble rock layers eventually collapsed to form a large complex of narrow tunnels and enormous caverns. The entrance to the cave is divided into two by a thick column of rock. It leads down into a gigantic tavern, large enough to park a cavalcade of ninety school buses comfortable. Referred to as the Twilight Zone, this huge foyer is 122m long and 45m wide. Deeper in the cave the walls and ceilings of the various passages and caverns have rich warm colours and intricate frieze-like patterns, created over centuries by water erosion and tumbling rocks and sand. The total length of the cave, including all its passages, is 4.5km. Its entrance is at the top and it descends to a few degrees, and the relative humidity varies between 67% and 93%.

HISTORY OF THE CAVE  | It is regarded as unlikely that Arnhem Cave was ever inhabited by prehistoric people. The first freehold owner of the farm, Daniel Bekker, discovered it in about 1930. A mining claim was soon registered to extract the nitrate-rich bat guano. One of the original claim markers can be seen painted on the rocks left of the entrance. The hoist platform inside dates from this period the caves were discovered. The guano was sieved to remove stones and gravel, and bags ere filled manually. A railway line was used to remove the full bags from the cave. Since the 1930s several entrepreneurs have mined guano at various times. It is estimated that there is currently a deposit of roughly 15 000 metric tons of guano in the cave.

THE BATS  | Six species of bats have been recorded at Arnhem, including the giant leaf nosed bat. Weighing up to 150gm and with a wingspan of more than 60cm, this is the largest insect-eating bat in the world. Sundevall’s leaf nosed bat is considerably smaller and can be seen in most parts of the cave. Other species are the long fingered bat, which roosts in dense colonies; the Egyptian slit faced bat with its distinctively large ears, Geoffrey’s horse shoe bat recognised by its characteristically shaped nose and the smaller Dent’s horse-shoe bat, which roosts in deeper parts of the cave. Other interesting cave dwellers include porcupines, musk shrews, bat parasites, pseudo scorpions and several species of spiders, beetles and crickets.