In Egypt, archaeologists are baffled by a mysterious structure believed to be the remains of an ancient pyramid that once stood over 200 feet tall—raising the puzzling question of who could have dismantled such a massive monument and reused its stones to build others. See more in Season 21, Episode 2, "Egypt's Lost Pyramid." Watch new episodes New Episodes Thursdays at 9/8c 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.