Welcome to the era of the megacity. More than half the global population now lives in urban areas, and there’s no going back to the farm. With China leading the way, today’s global cities are surging ahead in population and economic heft, powering the world economy — and posing some very difficult problems for governments. But it’s not all about the Beijings, the New Yorks, and Tokyos. Drawn from the McKinsey Global Institute‘s index of the world’s 75 Most Dynamic Cities, some of these up-and-coming commercial hubs — including Belo Horizonte, Fuzhou, and even Philadelphia — may surprise you. How many can you honestly say you’ve heard of, or visited?