Nantong, China

With a population of over 7.7 million, Nantong is no sleepy backwater. This sprawling industrial hub on the Yangtze River Delta has transformed itself in recent decades, emerging as a major manufacturing center and magnet for foreign investment. Yet the rapid growth has come at a cost - the city's once-pristine waterways now suffer from rampant pollution, and navigating the local bureaucracy can be a persistent headache. For those drawn to Nantong's economic opportunities, the tradeoffs may be worthwhile, but the city is certainly not for the faint of heart.