Ancient Aliens explores the controversial theory that extraterrestrials have been visiting Earth for millions of years. This new season Ancient Alien theorists show similarities between ancient structures built on opposite sides of the Earth that could prove to have been constructed or designed by aliens. From the age of the dinosaurs to ancient Egypt, from early cave drawings to continued mass sightings in the US, each episode in this hit History Channel series gives historic depth to the questions, speculations, provocative controversies, first-hand accounts and grounded theories surrounding this age-old debate. Did intelligent beings from outer space visit Earth thousands of years ago?