Just a pile of rubbish? Would you believe that it's actually a US Army HQ during World War II, disguised by architect Sir Basil Spence?
StrangeHarvest has a couple of interesting photos of such military deceptions from Masquerade: The amazing camouflage deceptions of World War II by Seymour Reit.
(If you're into this sort of things, definitely check out Jasper Maskelyne, a magician turned military camouflage genius who built fake tanks and even a fake city to trick German bombers during WWII)