Nabta Playa: 7,000-year-old astronomical site

Nabta Playa is a 7,000-year-old stone circle in southern Egypt, older than Stonehenge.

Built by ancient Sahara herders, it likely tracked the summer solstice and seasonal rains.

The site sits near an ancient lake basin, 100 km west of the Nile Valley, when the Sahara was greener.

Stone alignments suggest it is one of the world's earliest astronomical sites.