There's a very interesting piece in today's New York Times about the vacant lots in Cleveland, my hometown. (OK, my hometown was actually a suburb, but I still identify, for better or worse, with the "metropolis.") Anyway, there are enough of these lots now to constitute an actual ecosystem, and naturalists are studying it.
The article and the photographs convey the sadness of the city's long, probably permanent decay. But you can also see the charm: the brick buildings, the old broad-leaf trees, the mugginess--not always awful--of the summer air.