WUHAN, China - In the seven years it will take New York City to build a two-mile leg of its long-awaited Second Avenue subway line, this city of nine million people in central China plans to complete an entirely new subway system, with nearly 140 miles of track.

And the Wuhan Metro is only one piece of a $120 billion municipal master plan that includes two new airport terminals, a new financial district, a cultural district and a riverfront promenade with an office tower half again as high as the Empire State Building.

The construction frenzy cloaks Wuhan, China's ninth-largest city, in a continual dust cloud, despite fleets of water trucks constantly spraying the streets. No wonder the local Communist party secretary, recently promoted from mayor, is known as "Mr. Digging Around the City."

The plans for Wuhan, a provincial capital about 425 miles west of Shanghai, might seem extravagant. But they are not unusual. Dozens of other Chinese cities are racing to complete infrastructure projects just as expensive and ambitious, or more so, as they play their roles in this nation's celebrated economic miracle.

In the last few years, cities' efforts have helped government infrastructure and real estate spending surpass foreign trade as the biggest contributor to China's growth. Subways and skyscrapers, in other words, are replacing exports of furniture and iPhones as the symbols of this nation's prowess.

But there are growing signs that China's long-running economic boom could be undermined by these building binges, which are financed through heavy borrowing by local governments and clever accounting that masks the true size of the debt.

David Fuller's view Many building booms have a history of ending badly, at least in the medium term. We can all think of examples in our respective countries of residence. London's Canary Wharf, for instance, although some years later it proved to be a great success.

Dubai is undoubtedly the best example from the previous decade of a building boom gone wrong. Marketed to businesses as a gateway between Europe and Asia, and to minor celebs and wannabes as tax haven, it was overwhelmingly dependent on foreigners who have little or no historic or cultural link to the region. They can leave at any time and many did, except for those unfortunate visitors who could no longer afford to settle their debts.

At least China has the population to fill its gleaming new cities, provided people can afford it. The cost of living is often a problem for these provincial cities and it will not be resolved overnight.

Nevertheless, a city is dysfunctional without sound infrastructure. One can think of many cash-strapped municipalities around the world, not least in the west, and if they lack good infrastructure it is very difficult to attract the corporate presence required, not to mention tourists, all of whom will invest and support the local economy, creating jobs and future prosperity.

It will be fascinating to see how this building boom plays out over the next decade or more. At least China has two big, home grown advantages - an increasingly confident and ambitious population, and a very wealthy central government. It also continues to attract a considerable amount of foreign investment from the world's cash-rich multinational companies.