Scientists have confirmed that an assembly of huge stone slabs in Egypt's Sahara Desert is the oldest known astronomical alignment of megaliths in the world. Known as Nabta, the site is 6,500 to 6,000 years old, predating Stonehenge and similar prehistoric sites by about 1,000 years.

The site consists of a 12-foot-in-diameter stone circle, a series of flat, tomblike stone structures, and five lines of standing and toppled megaliths. Some of the slabs are nine feet high. Two sets of slabs are aligned in a north-south direction, while another pair provides a line of sight toward the summer-solstice horizon. An east-west alignment of megaliths is present, as are geometrical lines involving about a dozen additional stone monuments, the significance of which is not understood.