There are numerous historical, religious and mythic accounts of ancient civilizations being wiped out by volcanoes, earthquakes, floods, and meteors. See more in Season 2, Episode 6, "Alien Annihilation." Watch your favorite episodes of Ancient Aliens on The HISTORY Channel website at ...

If extraterrestrials influenced human history, can evidence of their existence be found in hidden tunnels and caverns around the world? See more in Season 2, Episode 4, "Underground Aliens." Watch your favorite episodes of Ancient Aliens on The HISTORY Channel website at ...