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.

Ancient Aliens has followed investigators across the globe as they've gone directly to the sites where signs of alien life have been found. Now, Giorgio Tsoukalos takes a look back at the most incredible evidence ever uncovered that could offer definitive proof that we are not alone in the universe.