The Celts lived across most of Europe during the Iron Age. Several hundred years before Julius Caesar, they occupied many parts of central and western Europe, especially what are now Austria, Switzerland, southern France and Spain. By the mid-1st millennium, with the expansion of the Roman Empire and migrating Germanic tribes, Celtic culture had become restricted to Ireland, the western and northern parts of Great Britain (Wales, Scotland, and Cornwall), the Isle of Man, and Brittany. I don’t think I’m the only person who thinks of the British Isles when I hear the word Celts.