Its schools and universities enable the city to join the intellectual conversation that is shaping the century. Its political and societal structure - city government, of course, but also its communities, its people, its think tanks, foundations, and other non-governmental players - decide how the city engages with the world. Its commercial power and reach establish its global reputation.

A city and its global status rest on four pillars - economic, political, educational and cultural. But there is more to a city than its economy. The global economy created global cities, and any discussion of a global city must focus on where that city fits into the global economy. If the true measure of an economy is the well-being of the people who live within it, the evolution of global cities is the key issue of our time. If we live in a city that aspires to become or remain a global city, we must grasp what makes these cities global and what makes them different - who lives in them, how they live, how they nurture their own citizens and relate to other global cities. To understand the 21st century, we must understand global cities. Like giant magnets, these cities draw the best and the worst and stir them into an urban mix unprecedented in its complexity. These pathologies-inequality, terrorism, pollution, climate change, traffic in drugs and human beings, the stresses of immigration - are felt first and hardest in global cities. If global cities monopolize global power, they also struggle disproportionately with the pathologies of a new economy. These peaks are called New York, Tokyo, London. Global citizens stand on the peaks, talking with each other over the heads of everyone else below, in the rural hinterlands and post-industrial backwaters which the global economy has left behind. Rather, it’s a world of peaks and valleys.

In short, global cities are where the action is. Global culture throbs to the magnetic beat of global cities. These cities have the finest orchestras and museums, the best restaurants, the latest fads.

Global communications radiate from global cities. Their universities train the global citizens of the future, while their researchers imagine that future. Their corporate headquarters and global business services make the decisions that shape that economy. Their banks and markets finance the global economy.

Culture definition global cities