Every year, a million visitors are drawn to the Salisbury Plain, in southern England, to gaze upon a mysterious circle of stones. Who built Stonehenge? What was it's purpose? a new generation of researchers is tackling these questions, finding important clues in the landscape surrounding Stonehenge - one of the densest concentrations of prehistoric stuctures in the world. The story of Stonehenge is being rewritten. Runtime: 60 minutes.