Detroit is only half inhabited by people. There are huge tracts of empty land dotted with abandoned factories and the facades of burned out houses. In many areas nature has started to take back the land leading to a baffling combination of decaying urban wasteland covered with neo-nature.
In some areas of the city wild turkeys, rabbits, and other unexpected wildlife roam through empty, broken up streets.
There has been talk of shrinking the city and using the deserted parts for farming, of all things. Here is an excellent article that describes the "right-sizing" of Detroit: http://www.freep.com/article/20090719/NEWS05/907190475/
Here are some random photos pulled off the web as an example:
This is just the tip of the iceberg.