Shanghai is the biggest construction site in the world. Frank McDonald, Environment Editor, went there to see its dramatically changing skyline and sample life at street level

There's one big difference between New York city and Shanghai. In New York, the skyscrapers are largely confined to Manhattan, whereas in Shanghai they're all over the place. And what's built already is only a foretaste of the future for this extraordinary Asian city that's rapidly re-inventing itself.

Architects and developers have had a field day in Shanghai since the Chinese government decided in 1990 to develop it as Asia's financial capital, in opposition to Tokyo and Hong Kong. They were presented with what was virtually a tabula rasa, or blank slate; the city and its skyline became their playthings.

Over the past 15 years, some 5,000 high-rise buildings (15 storeys or more) have been erected in Shanghai, including many that are much, much taller.

The pace and scale of the city's transformation is almost unimaginable until you learn that more than a quarter of all the world's tower cranes have been operating here.

Pudong, on the east bank of the Huangpu river facing Shanghai's famous Bund, was occupied by little more than rice paddies until it was designated for mega-development in 1990. Now, so many skyscrapers have been built there that it's sinking under the weight of concrete by 50 milimetres (two inches) every year.

The Oriental Pearl TV Tower is the gaudy symbol of this new Shanghai. With beetroot-coloured globes and tubular concrete legs, it rises to 468 metres (1,535ft), or nearly four times the height of Dublin's slender spire. It looks a lot better at night, putting on a sparkling light show that mimicks the Eiffel Tower in Paris.

Not far away is the city's finest skyscraper, the Jin Mao tower, which is also China's tallest building; literally, its name translates as "Gold Luxuriance". Though designed by international architects SOM, its form subtly refers to ancient Chinese pagodas, tapering as it soars to 88 storeys and topped by a distinctive emblem.

The 555-room Grand Hyatt starts on the 52nd floor and rises 35 storeys, gathered around a vast beehive-like atrium ringed with balconies; it claims to be the highest hotel in the world in terms of distance from ground level.

The view of Shanghai from any of its restaurants is almost surreal, like a diorama.

The Jin Mao is set to be surpassed by the 95-storey Shanghai World Financial Centre which, at 492 metres (1,624ft), will be the world's tallest building (however briefly) when it is completed in 2007. A sculpted glass tower that tapers to a single horizontal line, it will also have a luxury hotel on the upper levels.

Designed by New York-based architects Kohn Pedersen Fox (KPF) for the Japanese Mori corporation, its most controversial feature was a huge circular cut-out near the apex, which super-sensitive Chinese saw as a representation of the red sun on Japan's flag; this has since been changed to incorporate an enclosed catwalk.

Numerous other high-rise office towers have already erupted in the financial district of Pudong - billed as "China's Wall Street" - but the boulevards on which they're built are all far too wide and the public spaces so exploded that the area seems rather arid, which is odd because Richard Rogers was its master-planner.

Although most of the imposing stone façades of 1920s and 1930s buildings along the Bund are protected, some of their interiors have been re-modelled to create designer shops and restaurants. An eight-lane highway separates them from the riverfront promenade, forcing pedestrians to use tunnels to reach it.

On his visit to China last January, Bertie Ahern said he would like to have the powers of Shanghai's mayor, Han Zheng: "When he decides he wants to do a highway and if he wants to bypass an area, he just goes straight up and over." Well, not quite; some of the elevated freeways skirt surviving buildings by inches.

Whole swathes of Shanghai have been cleared to make room for freeways, high-rise office blocks, luxury hotels and shopping malls. Bamboo scaffolding around older buildings usually means they are about to be demolished, rather than revovated - and there isn't much residents can do to save their communities.

About 100 people who had got eviction notices protested recently outside the local Communist Party offices near the Ritz Carlton hotel on Nanjing Xi Lu - now as swanky as Madison Avenue - but the demonstation was quickly dispersed by police; in a totalitarian society, ordinary citizens have no power to change things.

It was by going to the Urban Plan Exhibition Hall on Renmin Square that many of them first discovered that their neighbourhoods were to be swept away. For here is housed a vast 1: 2,000 scale model of the planners' stunning vision of how Shanghai will look in 2020 - evoking, for all the world, Fritz Lang's Metropolis.

Maglev trains whisk people in from Pudong international airport at a top speed of 431km per hour, covering 31kms in just eight minutes. It seems very environment-friendly until you discover that the German-engineered project - which cost $2 billion (€1.6 billion) - is backed by a coal-fired power station. The airport, opened in 1999, was designed by French architect Paul Andreu.

Another compatriot, Jean-Marie Charpentier, designed Shanghai's Grand Theatre on Renmin Square - China's first purpose-built opera house - and was also responsible for remaking part of Nanjing Lu as a pedestrian shopping street.

Renmin Square, a public park that includes the superb Shanghai Museum of antiquities, is fringed by skyscrapers of every shape and size - a sort of architectural topiary. The most eye-catching by a long shot is Tomorrow Square, topped by what looks like a metaphorical granite head and forearms raised in prayer.

Designed by US architects John Portman & Associates, who created the early Hyatt atriums, it stands 285 metres high and is occupied by a Marriott hotel, offices, shops, restaurants and the highest apartments in Shanghai.

The unusual structure was challenging to build as it turns diagonally two-thirds of the way up.

Not far away is Xintiandi, a five-acre quarter of "renovated" (really rebuilt) low-rise brick shikumen houses, including one modest building where the Chinese Communist Party was founded in 1921. Now filled with bars, boutiques, cafés and restaurants, it's a bit like Temple Bar and much busier at night.

The most charming part of Shanghai is the former French Concession, a genuine relic of the city's colonial past. Here is where Sun Yat Sen and Zhou Enlai lived; their villa-style houses, just a stone's throw from each other on Sinan Lu, are open to the public. But what makes the area so attractive is its street life.

"The food vendors on the sidewalks, the small messy shops and holes in the walls, the markets selling flowers, antiques and curios, the interesting restaurants," as former Toronto mayor John Sewell eloquently put it.

Will all of this be cleared away by the planners as Shanghai prepares to host the World Expo in 2010? There has to be a bottom line. Because however arresting and photogenic the city's skyline may be, real urban life is not created by high-rise buildings alone.