Sinking feeling of a towering city

Shanghai is changing its skyline at an unprecedented rate. According to a report released last month by the Council on Tall Buildings and Urban Habitat, which studies and reports on all aspects of the planning, design and construction of tall buildings, Shanghai has become the 4th tallest city in the world, with 21 buildings taller than 700 feet (213.36 m).

In 1999, Shanghai completed the 88-floor, 420-m Jin Mao Tower, with a stainless steel pagoda-like design. It was Shanghai's first building taller than 700 feet, then the tallest building in the city. Since then the city has built 20 more super-tall buildings.

Shanghai's construction boom has come at a price. Owing to its location on a low-lying alluvial plain near the mouth of the Yangtze River, sinking ground levels have long been a headache. Although the main culprit has traditionally been the over-pumping of ground water, rapid construction of skyscrapers is increasingly playing a role.