The Streets of Philadelphia
This isn't Detroit or Newark, which are dead cities, or Cleveland, which despite heroic attempts to recreate some sort of downtown, is near dead. But it's hollowed out. Get the feeling that most who could moved out to the suburbs in the 1960s or whenever, and are in no hurry to move back. And they don't visit too often.
There is a lot worth seeing here, though, and I want to explore it a lot more. I don't even mind the occasional aggressive panhandler. I remember pre-Giuliani New York very well, and the street smarts are still here.