The interesting part about Detroit, amongst others, is that Detroit's "ruins" are due to an exodus of industry and followed by population. That's to say, it's not exactly due to gov't mismanagement or some kind of systemic failure. The failure is more individual --for example, company goes bankrupt --leaves building. But no one comes in to rent the building out. In other cases, it's due to buildings reaching their useful life --and not getting torn down properly (in this case, too costly for the gov't since no one is willing to build, as they would in other cities). All this is aggravated by the flight form the city to the suburbs and elsewhere. To put it succinctly, this is more organic, than artificial.

So, for example, you could be in a nice building and look across the street and look at a dilapidated building in disrepair. It's a weird juxtaposition but one shaped by economics and demographics.