The outstanding importance of cities as nodal points of a world-wide network was recognized by Peter Hall back in 1966. Since then, most of the research conducted on cities or city regions has focussed primarily on the world’s leading financial and economic centres (i.e. New York, London, Tokyo, Frankfurt) and on their role in a network of globally connected cities (Sassen, Friedman). While the outcome of these pioneering projects has provided researchers with valuable insights, research on the changing role of larger cities in the developing world is less advanced – despite the fact that urban growth rates in these cities are much higher than in the cities of the north. According to the UN, twenty-four of the thirty largest cities or city regions will be located in less developed countries by 2015.
The challenge of conducting research on large and important cities is that the significance of any given city is defined very differently by the authors of various studies. This divergence of views reflects both the diverse nature of cities and also differences of approach taken in the study of cities. In this section, we provide a short overview of the different understandings of the significance of large cities by introducing the terms world city, global city, informational city, mega city, and global city-region. Of course this is only a narrow selection made from a wide range of terms used to describe cities. However, in the context of our own study on Global City Regions as Changing Sites of Governance, we consider the following definitions to be extremely valuable for developing a framework of analysis.
Sassen (1991) defines global cities as, "cities that are strategic sites in the global economy because of their concentration of command functions and high-level producer service firms oriented to world markets; more generally cities with high levels of internationalisation in their economy and in their broader social structure". Thus, they are both centres of production and innovation as well as a home to markets. Manuel Castells describes the new urban phenomena as the informational city, adapted to his global information society concept. The key issues within his definition are the new communication technologies and infrastructure. This includes information technology, telecommunications, air transportation, and the accordingly necessitated infrastructure. Furthermore, he takes financial and economic performance into consideration. The informational city is to be seen as embedded in a global system of networked information flows.
These city-regions are expanding vigorously, and they present many new and deep challenges to researchers and policy-makers in both the more developed and less developed parts of the world. The processes of global economic integration and accelerated urban growth make traditional planning and policy strategies in these regions increasingly inadequate, while more effective approaches remain largely in various stages of hypothesis and experimentation. Global City-Regions represents a multifaceted effort to deal with the many different issues raised by these developments. It seeks at once to define the question of global city-regions and to describe the internal and external dynamics that shape them; it proposes a theorization of global city-regions based on their economic and political responses to intensifying levels of globalization; and it offers a number of policy insights into the severe social problems that confront global city-regions as they come face to face with an economically and politically neoliberal world.