Concrete circles marking old airfields

[Dana]

In Canada, WW2 brought about the Commonwealth Air Training Plan. There were many training bases built across the prairies, and the triangular runway layout was the thing. These are still seen from the air in many places

Quite common on this side of the border as well. Just for one example that I'm familiar with, Orange County Airport (KMGJ) in NY. One of the old runways is now the ramp and the others have been extended, but the shape is still there:

 

[iamtheari]

I-10 Exit 120 in Arizona is now named Verrado Way, but until a few years ago it was named Airport Road for the preexisting street south of the interstate. The airport in question was one of Luke AFB’s auxiliary fields, long closed. (Some others were kept alive, such as the present day Buckeye Municipal KBXK.) You wouldn’t notice it from the ground (and for all I know, not going that direction for a long time, it may now be a self storage facility or dollar store) but the triangle runway pattern was very obvious in Google Earth.

Archaeology is fascinating, no matter the time scales involved.