The ruins of Detroit, a series of photos by Yves Marchand & Romain Meffre documenting vacant buildings in Detroit. Some of the photos are repeated with useful annotation in this Time photo gallery. (See also Brian Ulrich's Stores That Are No More.)
On the other hand, some are arguing that there is great opportunity in Detroit right now.
Detroit right now is just this vast, enormous canvas where anything imaginable can be accomplished.