Adam’s Calendar, which may be the oldest artificial structure still standing, was discovered entirely by chance in 2003. 
When he lost control of his jet, a South African pilot named Johan Heine was flying above the Mpumalanga region, a hilly area in the country’s east.
His jet crashed into a mountainside after being forced to make an unscheduled landing. Heine narrowly escaped injury and emerged from the plane to see three massive dolomite stones in front of him. These gigantic stones protruded from the ground, each weighing roughly five metric tons (5.5 US tons). In front of them stood a massive stone circle.
The facility is located in an isolated region, with just a few dirt roads providing access. It would likely have remained concealed if the pilot hadn’t discovered it crash-landed.
But what Heine had discovered was remarkable. The megalithic structure appeared to be a very ancient stone calendar, and it was given the name “Adam’s Calendar” in honor of its great age.
Stonehenge in Africa
The pilot had spotted what seemed to be the world’s oldest artificial building. According to some theories, the site was built 300,000 years ago, well before any other indication of human civilization. If the monument is genuinely that old, it would rewrite human history and almost definitely necessitate the participation of a sophisticated civilization in its creation. Some have speculated that ancient aliens were involved in its construction, using this as a starting point.
An outer stone circle with a diameter of 30 meters (98 ft) surrounds the location. Several monoliths are positioned in a sophisticated design inside the ring. The site’s overall layout appears to be based on astronomical alignments, effectively turning it into a calendar.
