A volcanic island half a billion years old, Ailsa Craig has borne witness to countless events throughout history and prehistory from its station in the Firth of Clyde. Once a haven for Roman Catholics during the 16th-century Scottish Reformation, the island was quarried for its rare stone in the 19th and 20th centuries. Long ago disused and utterly uninhabited, Ailsa Craig still stands 11 miles out to sea, presiding over the links at Turnberry, another of its mysteries.