Hidden Cities Built Underground? (S4, E2) | Cities of the Underworld | Full Episode

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Don explores top-secret military and government tunnels and looks into classified technology that could be used to build entire cities...right under our feet. See more in Season 4, Episode 2, "America's Military Underground." Watch all new episodes of Cities of the Underworld, returning soon, and stay up to date on all of your favorite The HISTORY Channel shows at history.com/schedule. #CitiesoftheUnderworld Subscribe for more from Cities of the Underworld and other great The HISTORY Channel shows: http://histv.co/SubscribeHistoryYT Check out exclusive The HISTORY Channel content: History Newsletter - https://histv.co/newsletter Website - https://histv.co/History Facebook - https://histv.co/Facebook Twitter - https://histv.co/Twitter The HISTORY® Channel, a division of A+E Global Media, is the premier destination for historical storytelling. From best-in-class documentary events, to a signature slate of industry leading nonfiction series and premium fact-based scripted programming, The HISTORY® Channel serves as the most trustworthy source of informational entertainment in media. The HISTORY® channel has been named the #1 U.S. TV network in buzz for seven consecutive years by YouGov BrandIndex, and a top favorite TV network by Beta Research Corporation. For a deeper dive, visit history.com or follow @history on Instagram, Twitter, Facebook, YouTube and TikTok.