The spacious duplex comes with crocodile-skin bedposts, hand-carved bronze doors inlaid with Swarovski crystals — and a $45mn price tag. It is still on the market, but Charles Tong, the developer of Tomson Riviera, a luxury riverfront complex in the heart of the financial district here, says he is having no trouble finding takers for similarly priced units. “We’re selling three to four apartments every month,” said Tong, seated in a white Versace easy chair. “Now, people here want something more luxurious; they’d like a new lifestyle.” Everyone agrees China is in the middle of a spectacular real estate boom. The question is whether it is in the middle of a rapidly growing real estate bubble. When other recent booms collapsed — in the United States, for instance — they depressed entire economies. In China’s case, a bursting bubble could affect much of the world. China is the fastest-growing large economy and, so far, a main engine pulling the world out of recession. Beijing is clearly concerned. Authorities have recently moved to rein in the easy credit that has helped finance China’s hyperdevelopment, including making it more difficult for home buyers to take out a second mortgage. Last year, a record $560bn of residential property was sold in China, an increase of 80% from the year before, according to government statistics that are widely considered reliable. And with prices soaring, developers are scrambling to build more mansions, villas and high-rise apartments with names like Rich Gate, Park Avenue and Palais de Fortune. Signs of exuberance are everywhere. An investor in Shanghai recently bought 54 apartments in a single day; a villa sold for $30mn last year; and in December a consortium of developers paid more than $3.5bn for a huge tract of land in Guangzhou, one of the highest prices paid for any property, anywhere. In the city of Tianjin, in north China, developers have created a $3bn “floating city,” a series of islands built on a natural reservoir, featuring villas, shopping malls, a water amusement park and what they say will be the world’s largest indoor ski resort. “This is wild,” said Andy Xie, a former Morgan Stanley economist who is now an independent analyst. “By all the traditional measures, like rental yield, this is a bubble.”