The Ancient Astronaut Theory: the idea that extraterrestrials visited Earth in ancient times, influenced ancient cultures in many ways, and departed, i.e. the themes of authors Erich von Daniken, Zecharia Sitchin, Maurice Chatelain, John Michell, R.L.Dione, John Cohane, etc. The theory is based on ancient religious and secular literature and ancient megalithic construction and ground drawings around the world.