This is a remnant of one. We're pretty sure it's now just filled with used condoms and homemade crack pipes.
But in fact, the Allies soon realized that all of those airfields, complete with runways, fake aircraft, and buildings, were nothing more than elaborate props that could be defeated by an army of termites. The only thing left was to figure out the best way to let the Germans know that they weren't fooling anyone (in the most sarcastic way possible).
So the Allies flew bombing raids over these fake wooden airfields, presumably sending the German fake (wooden?) ground crews scrambling for cover. After several intense minutes in which nothing happened, the Germans finally realized what the Allies were doing: They were dropping fake wooden bombs on them.
"We need a volunteer for a highly classified mission. Who's good with a lathe?"
Just to make it absolutely clear to the Germans what was going on, many of these bombs had the phrase "Wood for Wood" painted on them. Yes, what the military calls "psychological warfare," the rest of us call "being a smartass."