Adam's Calendar: World's Oldest Man-Made Structure

South Africa's Adam's Calendar is believed to be over 75,000 years old, making it the world's oldest man made structure and significantly tens of thousands years older than Stonehenge and the Pyramids of Giza.
This makes it the world's oldest astronomical calendar and suggests that there may have been ancient cultures that were far more advanced than previously thought
The site is also believed to have been used for sound healing purposes among other great Mysterious things.