The Giant's Causeway on the coast of Antrim is a strange and marvellous sight. Was it the work of Fionn Mac Cumhaill, the legendary Irish hero, as many believe? If so, why did he build it? Was it for love, or was it for the challenge of a good fight against a powerful enemy? Or was the Causeway, as scientists think, the work of a volcano long ago? Which holds the truth science or legend?