It is amazing the innovation that goes on during times of war and the speed at which tasks get done.
I'd never heard of this one but apparently during WW2 the Boeing factory in Seattle was hidden by building a fake town on top of it. Fake, houses, fake trees, fake roads.
https://www.jalopnik.com/1936811/boeing-hid-factory-wwii/
Geffers
That is a fascinating find to learn about Boeing. They went through a lot of trouble to create the camouflage for their facility. Impressive war-time strategy.