Bothongo WonderCave

The Bothongo WonderCave in Kromdraai, Gauteng, South Africa is situated within the Bothongo Rhino & Lion Nature Reserve in the Cradle of Humankind, a UNESCO World Heritage Site. The cave is the third-largest cave chamber in the country. It is 5-10 million years old. The single chamber has an area of 46,000 square metres, and is 125 by 154 metres.

It was discovered in the late nineteenth century by miners who dynamited and excavated limestone for the making of cement. Mining stopped during the Second Boer War and never resumed.

Source: Wikipedia