The openstreetmap gives you a clearer overview of the cities. Each zoom step shows a different aspect (from density via main traffic to streets). On the right you should click on the plus, try the different layers to get more information. Choose the cycle map to get out all the level lines. It s even possible to export stuff.
Here you get help on how to use it.
There is a special Congo-Kinshasa Project. Maybe you could contact the user Moyogo or Olivier Auber.
Rio de Janeiro
TIJUANA: Thus-far mapped by user(s): Bman, AdamGeitgy.
San Diego has already its own page.