China is building up large collection of biggest things in world. latest addition is world's largest building. It is called New Century Global Center and it opened this week in Chengdu, Sichuan province, in China's southwest. It is 500 meters long, 400 meters wide and 100 meters high. area inside covers amazing 1.76 million square meters. building is so big that 20 Sydney Opera Houses could fit inside. It is almost three times size of Pentagon in Washington, D.C. It took thousands of workers just three years to build enormous structure. center is an important part of plans to make Chengdu 21st-century city. It fits with city's slogan, "Chengdu – Can Do". inside of center is almost like small city in itself. There are around 400,000 square meters of shopping space, 15-screen IMAX movie theatre complex and ice rink big enough to hold international competitions. There are also offices, hotels, replica Mediterranean village and water park. building's owners hope it will attract business and tourists from across China and world. It is all part of wider plan to put Chengdu on global map. Around 14 million people currently live in city, but that is set to increase. city is also magnet for investment and is one of China's most important industrial regions. area is also home to world's largest giant panda nature reserve.