England's finest burial barrow (104 m x 23 m), dating from 3500 to 3000 B.C. The entrance at the east end is flanked by two giant sarsen stones. The passage, lateral vaults and the chamber at the far end are roofed with massive cap stones, supported on upright sarsens and drystone walling. Some 50 skeletons from the early Neolithic period were discovered in the vaults.