Most of Africa lies on a vast erosional surface, referred to as a peneplain. Huge boulders that resisted erosion sunk as the soil level decreased. As boulder came to rest on boulder, massive arrangements called kopjes were formed. A visit to the Eppworth balancing rocks outside of Harare provides lessons in geology and prehistory. The product of eons of wind and water erosion, these balancing rock formations served as home to the bushman tribes that left their legacy with rock paintings (below). Ultimately, the bushman population was displaced with the migration of the Bantu peoples from the north.