Economic diversity in (and around) cities

Every city I’m familiar with has some areas that are economically depressed, and not great places to visit, let alone live in. But there are also areas, often in the 'burbs, that are upscale and thriving. And of course, many areas in-between.

Are there any U.S. cities that don’t have one extreme or the other, cities that don’t have either a “bad” neighborhood or an upscale one?

How about non-U.S. cities? Even in third-world countries, are there still wealthier neighborhoods outside the squalor?

In the third world, there are definitely nice areas where the wealthy live much like they would anywhere else in the world.

Every city has something that can be considered a “bad area”, but how bad these are may be relative to the city as a whole. For example, San Francisco’s “bad areas” strike no fear in to my heart- you really have to get in to nearby cities to get to the really scary places.

It kind of boils down to the fact that cities need poor people, too. And those poor people have to live somewhere.

East St. Louis, IL doesn’t have any nice neighborhoods. Neither does Compton, CA. And there are no bad parts of Kenilworth, IL or Beverly Hills.

Admittedly these cities are embedded in larger urban areas.

For metro areas generally, Laredo and Brownsville in Texas are pretty uniformly poor.

I don’t think there are any 100%-upscale big cities. One would be a fun place to visit, though, if it existed.