China's tallest building, the 101-story Shanghai World Financial Center, will open to the public on Saturday, 14 years after its developer, visionary Japanese property tycoon Minoru Mori, began the project. Mori expressed relief Thursday at having finally finished the project after years of stop-and-go progress on what he says is the building with the world's highest rooftop, at 1,614 feet (492 meters), and highest observation deck, but said he was eager for more big projects. “We have started to explore possibilities,” the 74-year-old developer told reporters Thursday, adding that “We haven't made any decisions.” Mori acquired the Shanghai site in 1994 and began piling work in 1997 - just as the Asian financial crisis hit. The land sat idle until 2003. The project has hit the market at a time when the Chinese property market appears to finally have cooled after several years of torrid growth, although space is tight for top-grade office space - exactly what Mori has to offer. Mori Building Co., which holds 70 percent of the equity in the project, says the building's current occupancy rate is 45 percent and is expected to rise to 90 percent within one year. Tenants include top Japanese financial companies, such as Sumitomo Mitsui Banking Corp. and Mizuho Corporate Banking Corp., as well as BNP Paribas of France and Germany's Commerzbank AG. At $3 per square meter rent per day, space in the building is pricey. But Mori said he was confident that the market will hold up, despite signs of trouble for some local property developers. “Total office space in Shanghai is not so large,” he said. “There is not enough taking into account the business potential of the city,” he added. “If you supply a good space, then the demand will follow,” he added. From its 101st floor observation deck, with transparent patches of flooring that allow visitors dizzying views to ground level, the view of Shanghai is sweeping and spectacular, reaching far beyond the bristling skyscrapers that dominate the city's horizon. The silver spire of the 1,381-foot Jinmao Tower next door, formerly the city's tallest building, lies far below. Mori's visions of a “vertical garden city” have transformed his hometown Tokyo's landscape with mammoth, mixed-use redevelopment projects such as Roppongi Hills, Ark Hills and Atago Green Hills. “There's no other city as interesting as Tokyo,” he said. “We still plan other developments to totally transform the city.” But other Asian cities -Singapore, Seoul, Sydney, Dubai - also appeal. “We are looking at sites where we can realize our plans for vertical garden cities,” he said. “There are many interesting cities.” “Who needs us and who is ready to receive us? These are the questions we are asking ourselves,” Mori said. Mori said he already has offered proposals to revamp Shanghai's bland Lujiazui financial district surrounding the bottle-opener shaped tower into a multi-use zone, with shops and other attractions under a pedestrian deck of greenery. A “modest” art gallery and, later, a museum, are also under consideration, he said. “I believe that Shanghai in the medium term and long term is just beginning its true development as a global financial center,” Mori said. “I don't foresee it shrinking.” Over the years the project has gone through several major changes. After the Sept. 11, 2001, terrorist attacks in the United States, the building was redesigned into a so-called “megastructure,” with four huge pillars to make it stronger. The builders also altered the original plan for a circular cutout near the top - after complaints that it resembled the rising sun on Japan's flag, a symbol reviled by many Chinese because of Japan's brutal occupation of the country in World War II. Mori changed it to a rectangle. The building's height was raised to make it the world's tallest building, but it has already been surpassed. The Burj Dubai became the world's tallest building in July 2007. A few months later it became the world's tallest freestanding structure, when it passed 1,800 feet (548 meters). It is still under construction - its final height is a closely guarded secret.