Complex sentence: One of the world's oldest known archeoastronomical devices is located in the Nabta Playa basin.They were created by the ancient Nubians about 1000 years before Stonehenge, the device may have served as a prehistoric calendar, which accurately marked the summer solstice.
Split into simpler sentences: One of the world's oldest known archeoastronomical devices is located in the Nabta Playa basin. It was created by the ancient Nubians about 1000 years before Stonehenge, the device may have served as a prehistoric calendar, which accurately marked the summer solstice.