According to Harvard economics professor Edward Glaeser, "the city has triumphed". Despite the revolution in information and communication technology and cheap air travel, "more and more people are clustering closer and closer together in large metropolitan areas". In this compelling study of how economic forces shape our cities, Glaeser explains that it is the very closeness of urban life, the opportunity for face-to-face interaction, that makes cities such dynamic and exciting spaces which continue to attract both the poor and the wealthy. Of course, not all cities are thriving. Industrial cities like Detroit are haemorrhaging people. But Glaeser argues such single-industry cities contained the seeds of their own downfall. Diversity and competition are essential and he rejects attempts to reverse urban decline by building art galleries à la Bilbao as "edifice errors". Far better to invest in people's skills: "The real city is made of flesh, not concrete." For creativity, sociability and the love of new ideas lie at the heart of all successful cities.