There is a myth common to the ancient Celts of Ireland, Wales and Gaul that their descendants are people from the west, sometimes called Atlantis, known to others as Avalon. This myth of western origins is also found among Berbers of the north African coast and in Scandinavia, hardly surprising since they all share an Atlantic seaboard culture since Megalithic times.
Now it is generally agreed that the megalithic builders had an advanced understanding of astronomy and widespread common designs such as spirals, circles and lozenges, which some people think are maps of the night sky, the legends of a lost civilisation seem a little less outlandish.