The erection of monumental stones exists in many cultures around the world. But it is on the French Atlantic coast and in the United Kingdom that we find the most spectacular and ancient forms. Theories abound on the origin and significance of these stone giants. Surrounded by mysteries and legends, the megaliths attract scientists, artists, adventurers and enthusiasts from all walks of life. Are they the work of sorcerers or giants, or are they the manifestation of supernatural forces or extraterrestrial presence, as some think? Are they simply an illustration of a critical turning point in the history of humanity and the birth of our modern culture? Whatever the theory, they always ask the same questions: who erected these monumental blocks? When? How? And why?