bourke's luck potholes in graskop, mpumalanga - popular geological attraction formed by water erosion

bourkes luck potholes blyde river canyon pot holes hole sandstone formation rock geology stone mpumalanga south africa nature water travel erosion bridge outdoors tour tourism destinations graskop popular tourist attraction province cliff geologic pothole waterfall vacation escarpment bedrock adventure cascade footbridge stream body bourke#39aph39#s geological formed