When one billion rural Chinese move to cities, our planet will change irreversibly. Finnish professor Eero Paloheimo and Chinese business magnate Zhang Yue are going to save the world by reinventing the city. Their utopias are very different: Zhang plans to build the tallest and most ecological building on Earth, an Eco-city in the shape of a skyscraper, built at world record speed. Paloheimo has designed a unique clean-tech test laboratory city, and struggles to get it built in a flourishing valley outside Beijing. Is the future of urban mankind in the cherry valleys of China or high up in the sky?—Anonymous