If China's state planners have their way, Northeast China will soon be home to a massive regional hub with a population five times that of the New York metropolitan area.

Officials hope the Jing-Jin-Ji region — shorthand for Beijing-Tianjin-Hebei, the three areas that they plan to grow increasingly integrated — will become an immense megalopolis to rival any in the world. (Ji is a one-character abbreviation often used for Hebei province.)

Together, the three regions have a combined population of more than 100 million, or some 10% of China's one billion-plus people.

There has long been talk of integrating the three, with no less than President Xi Jinping calling for a regional economic hub comprising the three regions in late February. Their populations already mix considerably: some one-fifth of Beijing's nonresident population hails from Hebei, a poorer, steel-producing province roughly the size of Oklahoma. Tianjin was connected to the capital via a high-speed train in 2008 that covers the 130-kilometer (80-mile) distance in a mere 30 minutes. Officials hope that further integration of the areas will spur more development as well as help to relieve Beijing's belching smog, sprawling traffic jams and notoriously long commutes—which in some cases stretch to as long as three hours. Though Beijing and Tianjin officials have stayed tight-lipped on plans, Hebei stirred the pot last week when the provincial government announced on its website (in Chinese) that the city of Baoding was preparing to take on some of Beijing's administrative functions, without offering specifics. Housing prices in Baoding, which is about 150 kilometers from Beijing, have jumped in anticipation of such moves. According to data from real-estate services company E-House, Baoding property prices have risen nearly 5% in the past month—the highest spike in the nation over that period. "I went to look at an apartment in the morning. It was 4,300 yuan per square meter," said one Beijing resident who was shopping for apartments in Baoding last weekend. "By the next day, it was up to 5,100 yuan." But Jan Wampler, an MIT professor who has worked as an architect in China for many years, cautions against any rush to create a too-sprawling megalopolis. "I'm a great critic of the way Beijing has developed," he said. Beijing currently has six so-called "ring roads" that loop around the city's center—think D.C.'s Beltway—and a seventh is slated to open in 2015 that will connect it to Hebei province, according to state media. "You can't continue to build ring roads. It's got to stop sometime," said Mr. Wampler. "I think it's at a stopping point now." -- Te-Ping Chen, with contributions from Li Jie. Follow Te-Ping on Twitter @tepingchen

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