Beneath the surface of America lies a hidden world—literally. In this video, we explore 10 secret underground places in the U.S. that most people have never heard of. From Cold War doomsday ...

Built in 1942 on land seized through eminent domain, the concrete structures at Assabet River National Wildlife Refuge now ...

Hidden beneath the old bunkers at Fort Stevens State Park on the Oregon Coast is a network of long-abandoned tunnels built to defend the U.S. from its enemies.

During the Cold War, the U.S. built a military base under the ice in Greenland, hidden from the Soviets. It was eventually abandoned, but its most lasting legacy is a pivotal role in climate science.