Beneath the jungles of Mexico, archaeologists uncover a cave hidden for centuries—one unlike any other—raising questions about a lost underground Mayan temple and the secrets it may still hold. See more in this clip from Season 2, Episode 4, "Underground Aliens." Watch an all new season premiering Friday, August 29th at 9/8c. 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 HISTORY Channel shows: http://histv.co/SubscribeHistoryYT Find out more about the show and watch full episodes on our site: https://histv.co/AncientAliens Check out exclusive The HISTORY Channel content: History Newsletter - https://histv.co/newsletter Website - https://histv.co/History Facebook - https://histv.co/Facebook Instagram - https://www.instagram.com/history TikTok - https://www.tiktok.com/@history "Ancient Aliens" explores the controversial theory that extraterrestrials have visited Earth for millions of years. HISTORY® 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.