Ancient Aliens has followed investigators across the globe as they've gone directly to the sites where unexplained incidents have been reported. Now, Giorgio Tsoukalos takes a look back at the most extraordinary encounters that, as far as he's concerned, provide evidence of an extraterrestrial presence on Earth.

Ancient Aliens has met with eyewitnesses and traveled to the sites of incredible UFO incidents reported all over the world. Now, Giorgio Tsoukalos takes a look back at the most compelling investigations of all, and events that he believes represent real encounters with extraterrestrial visitors.