"CARTWHEEL" Tower, Fort Reno, Washington, DC, 2020.All the pixels, none of which are concealing any secret communications networks, at flickr.com/photos/mattblaze/49#photography
@mattblaze Old telephone switching offices are a good example of hiding in plain sight, if you know what to look for; I doubt that one in a thousand passers-by noticed them when they were in use, even though they were typically in downtown locations, e.g. en.wikipedia.org/wiki/811_Tent