Ancient Aliens

If ancient aliens visited Earth, what was their legacy, and did they leave behind clues such as sophisticated aircraft, complex electrical grids and intricate construction machinery?

If ancient aliens visited Earth, who were they, and where did they come from? Possible historic evidence and beliefs from around the world are examined.

If ancient aliens visited Earth, what was their mission? From crop circles to hieroglyphics, evidence may exist in multiple cultures throughout history suggesting that aliens came here with a plan.

Reports of encounters with strange beings and sightings of mysterious objects have occurred throughout history. Could these sightings be evidence that aliens have been with us all along?

Did we experience alien contact in the 20th century? WWII Air Force planes were buzzed by mysterious balls of light, and the alleged crash of a flying saucer in Roswell launched the age of UFOs.

What if life on Earth began in outer space? Are monuments like Stonehenge and Easter Island the last remains of an ancient alien visitation? This special investigates.