Thought to have been used for purposes ranging from burial chambers to devices that tracked astronomical events, megaliths are the large stones found in the Neolithic through Bronze Age constructions of the world’s indigenous peoples. Though some megalithic structures are made of a single, freestanding stone, those built using multiple stones have stood without mortar or cement for millennia. What African megalith that predates Stonehenge by 1000 years is the oldest known astronomical device? Discuss