It may have been a tornado shelter as well. I didn't see any air handlers or anything so who knows?
My grandfather was an electrician that wired the missile silos along the front range.
They lived in the Springs and he said it was the best place to live if the Russians bombed us. With an Army base, two Air Force bases, the academy and NORAD, it was sure to be a high priority target. One big flash and that's it. Left a lasting impression on a 6 year old.