Some cities are more dynamic than others, some are more important, larger, or simply more urbane. And while there are any number of factors that determine a city's importance, be it economic or infrastructural, it can also be something less tangible, such as culture or history, or even freedom of expression, or quality of life. It is a well-known fact that the world is now 50 percent urban, but the idea that we can simply divide the world's population into urban and rural is too simple, too naïve. People who dwell in towns, even very large towns in rural India or China, lead a far less urbane existence than do farmers in Western Europe, say; and even the urban environment itself embraces a wide range of varying types: from the rural village to the glittering global metropolis. Urban fabric also contains a bewildering array of types, everything from the sleepy suburb to the twenty-four-hour dynamo that spins at a city's centre.

Cities are graded according to a wide variety of factors; one of the betterknown is the Globalization and World Cities (GaWC) Research Group’s ranking system. In this system the world's major metropolises are divided into alpha, beta, or gamma, with London and New York as alpha cities, Hong Kong and Singapore as beta, and Kuala Lumpur and Jakarta as gamma. This global grading system takes into account a number of important factors and yet all it is doing is reflecting the sophisticated and highly ordered system of self-organization that operates between these cities. In many ways this is much the same as the way in which cities organize themselves internally, by a sort of autopoesis.

One thing nearly every city has in common in the twenty-first century is that they will be interacting ever more closely in an increasingly globalized economy. What makes this interaction particularly vital is the fact that this global economic system has become more and more homogenized simply because it has no real alternatives: China's embrace of capitalism in the 1970s followed by the collapse of Soviet-style economics in the 1990s means that the world can be said to operate one economic system, i.e. that of global capitalism. And yet globalization is not quite as new as some may think.