Just before I got on the plane for Istanbul, I prevailed on a professor friend of mine to come with me to Detroit's abandoned Packard factory. Built 1907-1909 by Albert Kahn, it was maybe the world's first large reinforced concrete building. Now abandoned, its millions of square feet of empty space are a great place to watch the archaeological process at work.
Acres of rooftops are now home to tiny wetlands, complete with grass and birds:
Little forests are gradually wrestling the factory to the ground:
Leading to wonderfully atmospheric fourth-floor ruins.
Sometimes it takes on almost a Classical air:
The ruins of Detroit are, more and more, becoming sites of memory and nostalgia for white Michiganders who yearn for their lost industrial glory. Places like Packard are wonderfully well-documented with wonderful Flickr sets like this one, from my friend (and birthday twin) Pat. (I've put my own photos up here out of sheer vanity, but he's a much better photographer.) The old factory even gets the occasional weird recreational use - some people even organized a croquet game there once, in full Edwardian costume!