Ancient theorists meet in Santa Monica to decipher important cave art. See more in this clip from Season 1, Episode 5, "Mysterious Underground Worlds." Watch full episodes and stay up to date on all of your favorite shows on The HISTORY Channel website at http://history.com/schedule. ...

Reverence for the number three dates back thousands of years. What is it about this number that continues to fascinate mankind? The U.S. military has long denied that the infamous 1947 Roswell crash was anything other than a weather balloon. See more in Season 2, Episode 14, "Mysteries By the ...

Dive into the ultimate exploration of humanity's greatest mysteries! Are mass suicides and unholy rituals the result of extraterrestrial whispers? Could the legendary powers of ancient gods and today's super-heroes be rooted in alien technology? Find out in this full episode marathon of Ancient ...

Ancient astronaut theorists reveal the untold truths regarding Quetzalcoatl - the Mexican God. See more in this clip from Season 21, Episode 7, "Mysteries of the Aztecs." Watch full episodes and stay up to date on all of your favorite shows on The HISTORY Channel website at ...

Check out these unexplainable alien phenomena. See more in this Ancient Aliens marathon. Watch full episodes and stay up to date on all of your favorite shows on The HISTORY Channel website at http://history.com/schedule. #AncientAliens Subscribe for more from Ancient Aliens and other great ...

Check out these epic alien crashes. See more in this Ancient Aliens compilation. Watch full episodes and stay up to date on all of your favorite shows on The HISTORY Channel website at http://history.com/schedule. #AncientAliens Subscribe for more from Ancient Aliens and other great The ...

Egyptian hieroglyphs depict the use of light bulbs in tombs and secret chambers. See more in Season 5, Episode 3, "Alien Power Plants." Watch full episodes and stay up to date on all of your favorite shows on The HISTORY Channel website at http://history.com/schedule. #AncientAliens ...

Check out these amazing Machu Picchu connections. See more in this Ancient Aliens compilation. Watch full episodes and stay up to date on all of your favorite shows on The HISTORY Channel website at http://history.com/schedule. #AncientAliens Subscribe for more from Ancient Aliens and other ...

The Sumerians in ancient Mesopotamia achieved over one hundred "firsts" for human civilization. Advances in writing, agriculture, science, mathematics, medicine, astronomy, transportation, building, military, schools and city planning, all originated in Sumer. See more in this marathon from ...

Ancient astronaut theorists speculate the causes for mysterious disappearances and sightings at Skinwalker Ranch. See more in this clip from Season 21, Episode 8, "The Glowing Orb Phenomenon." Watch full episodes and stay up to date on all of your favorite shows on The HISTORY Channel website ...

Check out these epic doomsday theories. See more in this Ancient Aliens compilation. Watch full episodes and stay up to date on all of your favorite shows on The HISTORY Channel website at http://history.com/schedule. #AncientAliens Subscribe for more from Ancient Aliens and other great The ...

Ancient astronaut theorists explain the hollow earth theory. See more in this clip from Season 1, Episode 6, "Mysterious Underground Worlds." Watch full episodes and stay up to date on all of your favorite shows on The HISTORY Channel website at http://history.com/schedule. #AncientAliens ...