Did you hear about the guy who built a secret apartment inside a mall in Rhode Island? He even lived in the secret apartment for a few years until he was discovered and forced to move out.
He named the place, "Trummerkind" or "children of the ruins," a term for post-WWII orphans who had lost their families and homes and lived in the ruins.
So this guy is uber artsi-fartsy. Check out this tunnel secret installation thing he made.