Ancient underwater cities can be found around the globe, but could these aquatic worlds be the ruins of unknown civilizations--or even proof of extraterrestrial visitations? See more in Season 2, Episode 4, "Aliens Above and Below."
"Ancient Aliens" explores the controversial theory that extraterrestrials have visited Earth for millions of years.
The HISTORY Channel® is the leading destination for award-winning original series and specials that connect viewers with history in an informative, immersive, and entertaining manner across all platforms. The network's all-original programming slate features a roster of hit series, premium documentaries, and scripted event programming.