Each classification is based on a particular city's unique relationship to world markets, the national economy, and local or regional market activity. Three Classes of Cities Cities vary in size and function. The typology of global, national, and regional cities is adapted from Peter Hall's Globalization and the World Cities . Because today's economy is global, every city is part of a functional world city system. But global cities are at the apex of the world urban order and are qualitatively different from national or regional cities.
Global cities are epicenters of human activity that help drive the global economy.
Their businesses focus mainly on specialized information services, such as financial services, medical services, educational and health services, and tourism. They are also centers of cultural innovation, much of which finds its way into commerce. The global city is a place of very high density in terms of buildings and population. Businesses that thrive in a global city's downtown are information intensive and benefit from the proximity of similar businesses. Few cities are large and important enough to be considered global cities.