Shenzhen, Guangzhou, Dongguan—these words might as well delineate frozen Antarctic seas or label craters on the moon, so far has the voracious expansion of these Chinese megacities outpaced their name recognition. Their combined population of over thirty million drives “the workshop of the world,” a sprawling, hyper industrial megalopolis on China’s southeastern coast. Knowing that these places exist at all marks you out as either someone who makes iPods for a living, or a serious urbanist.

China’s megacities, like the topless towers of Dubai and the just-add-water culture capital of Abu Dhabi, make for breathless blogging and amusing cocktail chatter in the gentrified districts of “old cities” like New York, Zurich, and London. Indeed, China’s urban behemoths are a major reason why architects, planners, and bureaucrats are talking with renewed fervor about Cities with a capital C, after an era in which suburbs were cast as our inevitable future. Yet few non-Chinese have actually spent much time in the fluorescent-lit factory towns and stultifying malls of the Pearl River Delta, inhaling their thousand-tongued fumes or navigating their inhuman boulevards.

Even less is known of other megacities like Chongqing, Wuhan, or Tianjin. Are these dystopias to be avoided at all costs? Or have they rescued the very idea of urbanism, offering a twenty-first-century model of eco-dense community that can fix our “planet of slums”? Besides brief forays from nearby safe havens like Hong Kong and Shanghai—tidy, manageable, and English-speaking enough for Western tastes—we’ve been guided mostly by gorgeous computer-generated visualizations of the Chinese megalopolis, courtesy of real-estate developers and government offices.

In 1980, Shenzhen was still a sluggish cluster of small fishing villages and rice paddy communes just across the water from Hong Kong, the most densely packed city in the world. With a single policy stroke—gathering these sleepy hamlets into the country’s first Special Economic Zone (SEZ), in which restrictions on trade, foreign investment, and mobility were permanently suspended—Chinese leader Deng Xiaoping dramatically launched his policy of Reform and Opening, creating China’s first “window on the world.” Ever since Peter the Great broke ground on his instant city by the Neva, politicians have deployed new cities as policy instruments and self-contained experiments. China’s state-led industrialization in the 1950s and radical Maoism in the 60s dealt fatal blows to the traditional character of most its cities. Recent makeovers, just as total, have even-handedly effaced the last remnants of socialist city planning

Today, Shenzhen is a living, breathing expression of Deng’s triumphant market authoritarianism kept under close surveillance. A population of nine million souls officially—perhaps as high as twelve million in actuality—powers one of the largest urban economies anywhere, including the fourth-largest port in the world and 100,000 factories in the surrounding area. (Most of the world’s oil paintings, laptops, neckties, and socks are also produced on the southeastern coast.) Almost everyone is young and was born somewhere else; most are either highly educated or half-literate peasants. Throughout the 1990s the slogan was “one high-rise a day and one boulevard every three days.”

If Shenzhen was once everything that the rest of the country was not, today the whole country aspires to the condition of this sweltering Special Economic Zone on the South China Sea. The SEZ concept has been extended to dozens of cities and counties, prompting the most unstoppable wave of urbanization the world has ever seen. Last year, the consulting firm McKinsey estimated that 350 million more Chinese would move to urban areas by 2015, resulting in over 220 cities with populations of over one million people. Many villages already seem depopulated, places where only the old and ill remain. According to surveys, a large proportion of China’s peasants, numbering close to 800 million, would jump at the chance to live in a city.

Thirty years on, the new megacities are a marvel in some respects and a nightmare in others. Built for giants, they fly in the face of every New Urbanist lesson about liveable neighborhoods and community redevelopment that Westerners thought they had learned from bitter experience. These cities are the offspring of a marriage of convenience linking a single-party dictatorship and multinational capitalism, and the mixed parentage is apparent everywhere: official mandates and eminent domain trump all else, but industrial giants like Foxconn build cities within cities, local magnates throw up helter-skelter utopian schemes, and a floating population of migrant workers copes as best it can.

An intense chaos of disease, labor struggle, and economic competition is playing itself out, but these cities are far more orderly and comfortable than the slums of Mumbai; more compact and less car-dependent than LA or Mexico City, more humane than the favelas of Rio or the shantytowns of greater Johannesburg. They are witness to bold new experiments in architecture, clean energy, and public transportation, even as they recapitulate, in fast-forward motion, all that has been most frightening and abhorrent about urban existence for centuries.

More than anything, what cities like Shenzhen and Dongguan could use is a Chinese version of the “City Beautiful” movement, which brought progressive politics, public amenities, and healthier lifestyles to American cities toward the end of the nineteenth century. In China, “If you build it, they will come” has long been the watchword of local governments and developers: should the real-estate bubble burst, or the economy stop to catch its breath, the heroic age of instant cities could enter instant eclipse, making the ghost towns left by the resource and railroad booms in the American west look like small potatoes. The anonymous, bombastic skylines already loom dark with vacancies. Projects like Dongguan’s South China Mall, completed in 2005 by an instant-noodle billionaire on former farmland, are fateful failures: planned as the world’s largest mall, a microcosm of the world in seven massive zones, it lies 99 percent empty; only a dozen or so vendors still hawk their pathetic wares.

As the heroic age of the Chinese megacities passes into something more sober, Shenzhen and the others stand at a crossroads: can the Age of Socialist Construction give way to the Epoch of Maintenance and Repair? Can a “floating population” become a citizenry? Why do some instant cities last and others turn to dust?