https://youtu.be/X9JyiZ9Qkpg

Inside the hidden base still keeping an eye out for North Korean missiles https://amp.cnn.com/cnn/2018/05/11/politics/inside-norad-north-korea/index.html

North American Aerospace Defense Command (NORAD), the joint Canada-US organization tasked with warning of incoming threats from the sky, continues to monitor North Korea's nuclear program with the same intensity it did at the height of North Korea's missile testing. In fact, NORAD and US Northern Command Center Director Col. Travis Morehen, a Canadian, says the organization still gets three or four intelligence reports on the country's nuclear program every day.

Originally built during the Cold War to defend against Soviet bombers, it's now used to detect the latest missile launches abroad, and monitor potential threats to domestic air traffic.

The primary command center is located at nearby Peterson Air Force base, but in the event of a serious real-life nuclear threat, the operation would shift to Cheyenne Mountain, and for good reason. It's secured by two massive 23-ton blast doors, completely sealing it off from the outside world to survive a nuclear strike, or maintain communications after an electromagnetic pulse attack. Outside of training, those doors have sealed shut only once before: September 11, 2001.
The 15 buildings inside are built on 1,300 giant springs built to allow them to bounce in the event of a nuclear strike or earthquake. And inside the command center, there is enough powerful technology to detect a missile launch anywhere on the globe within seconds.