DEWLine Museum – The Distant Early Warning Radar Line

I think the most impressive part about these sites was the way they networked them together with UHF/Microwave Troposcatter links, which basically just scream RF into the sky and then listen for the small amount of energy that's reflected off the troposphere on the other end. (It's a little more complex than that)

https://en.wikipedia.org/wiki/Tropospheric_scatter

This method was the back-bone of long distance Cold War communications links (As well as HF using ionospheric propagation) until Satellites started becoming more commonplace in the 70's

meteor scatter communications were even more crazy and impressive (still in use actually)