Callanish Stones Isle of Lewis Outer Hebrides Scotland The Neolithic stone circle at Callanish Calanais dates from approximately BC It consists of a ring of stones of Lewisian gneiss the tallest of which marks the entrance to a burial cairn although archaeologists believe the cairn was a later addition to the site Various theories exist concerning the purpose of the circle and the nearby other rows and avenues of stones including the possibility that they functioned as a form of lunar calendar A local legend says that the stones are giants who were turned to stone by St Kieran when they refused to convert to Christianity