In both China and the Persian Gulf, cities comparable in size to New York have sprouted up almost overnight. Only 30 years ago, Shenzhen was a small fishing village of a few thousand people, and Dubai had merely a quarter million people. Today Shenzhen has a population of eight million, and Dubai’s glittering towers, rising out of the desert in disorderly rows, have become playgrounds for wealthy expatriates from Riyadh and Moscow. Long-established cities like Beijing and Guangzhou have more than doubled in size in a few decades, their original outlines swallowed by rings of new development. Built at phenomenal speeds, these generic or instant cities, as they have been called, have no recognizable center, no single identity. It is sometimes hard to think of them as cities at all. Dubai, which lays claim to some of the world’s most expensive private islands, the tallest building and soon the largest theme park, has been derided as an urban tomb where the rich live walled off from the poor migrant workers who serve them. Shenzhen is often criticized as a product of unregulated development, better suited to the speculators that first spurred its growth than to the workers housed in huge complexes of factory-run barracks. Yet for architects these cities have also become vast fields of urban experimentation, on a scale that not even the early Modernists, who first envisioned the city as a field of gleaming towers, could have dreamed of.