Nabta Playa was once a large internally drained basin in the Nubian Desert, located approximately 800 kilometers south of modern-day Cairo or about 100 kilometers west of Abu Simbel in southern Egypt, 22.51° north, 30.73° east. Today the region is characterized by numerous archaeological sites. The Nabta Playa archaeological site, one of the earliest of the Egyptian Neolithic Period, is dated to circa 7500 BC.
Located in Africa, Nabta Playa stands some 700 miles south of the Great Pyramid of Giza in Egypt. It was built more than 7,000 years ago, making Nabta Playa the oldest stone circle in the world — and possibly Earth’s oldest astronomical observatory. It was constructed by a cattle worshiping cult of nomadic people to mark the summer solstice and the arrival of the monsoons.
By the 5th millennium BC these peoples had fashioned what may be among the world's earliest known archeoastronomical. These include alignments of stones that may have indicated the rising of certain stars and a "calendar circle" that indicates the approximate direction of summer solstice sunrise.
"Calendar circle" may be a misnomer as the spaces between the pairs of stones in the gates are a bit too wide, and the distances between the gates are too short for accurate calendar measurements." An inventory of Egyptian archaeoastronomical sites for the UNESCO World Heritage Convention evaluated Nabta Playa as having "hypothetical solar and stellar alignments."
According to astronomy