There are only four major urban civilization recorded.

    * The middle-east from where most of us of advanced countries have inherited the concept... Tigres and Euphrates (The reference to Gilgamesh often seen as the father of the City concept or at least as it's vehicle in litterature).
    * The Indus and the Gange one (not yet fully recorded) with Mohenjo-Daro and now several cities discovered i what is also called the Harrapa civilization.
    * The Yellow river in China, Huanghe that is the Chines civilization cradle
    * The high plateau of Andes... (Uh???) Hey, how come? Where is the hot desert and the river ?... Well in South America the problem (as in France today) was more about the crop... Corn ! That is highly demanding of water! And on a limestone plateau that's not a simple task!

Could you comment a bit on why the city states of ancient Mesoamerica (e.g., Tical, Palenque, Montealban, Teotihuacan, etc.) don't count? Is it because the core function of these cities seems to have been religious and ritual? They were built around temples and other sites of worship and ritual, and while they usually developed peripheries of human dwellings (apparently housing tenths of thousands of people in some cases), housing a human population never seems to have been the primary function of these cities. Of course, it may be equally appropriate to view these as instantiating a radically different concept of the city - since they did develop a lot of the same structural features as cities in other places.

If you can't convince them, confuse them. (Harry S. Truman)