It was once thought the hill was a burial mound, but no grave has been found and its purpose is unknown.

BBC: Prehistoric Silbury Hill 'was built in layers'

"These stones may have provided an inspiration for the Barrow-downs, where the hobbits in The Lord Of The Rings are ensnared by a malevolent wraith that haunts a barrow or burial mound, " said Mr Garth.

BBC: Oxford