You probably already know that Cheyenne Mountain is where NORAD is located. It's an entire military base inside a mountain! I've been in there one time, long ago, to take a tour. I don't think they actually offer tours to the public, but my mom was able to get us in at the time because she had friends in high places, as they say. Later, after he retired from the Air Force, my dad worked at NORAD for several years as a civil servant.
Lately I've been binge-watching the '90s era sci-fi TV series "Stargate SG1", much of which takes place inside NORAD. It's pretty fun to see them using footage over and over of the actual road that leads into the mountain. It still looks the same!