China and other rapidly developing Asian nations are attracting cutting-edge international architects as their increasingly futuristic skylines offer the chance to push design boundaries. French architect Paul Andreu was handed what he calls a once-in-a-lifetime opportunity when Chinese authorities picked him to design an ultra-modern opera house in the centre of Beijing. \"I\'m grateful towards China,\" said Andreu, whose 300-million-euro ($430 million) opera house a rounded titanium and glass structure rises from a man-made moat next to the Forbidden City and Tiananmen Square. \"That was an opportunity that you only get once in your life, if at all,\" the award-winning architect, who is currently working on two other projects in China, told AFP. \"China is building a huge amount, so opportunities are huge. But China also has a lot of ambition. For years, they didn\'t do much, and I\'m sure they had the feeling they were lagging behind.\" Now, the Asian powerhouse whose breakneck growth over the past 30 years has transformed it into the world\'s second-largest economy and fuelled a colossal construction boom is making up for lost time. The 90,000-seat \"Bird\'s Nest\" stadium, which became the centrepiece of the 2008 Olympics with its threads of interlocking steel beams, is probably the best known of innovative structures that dot China\'s skyline. Beijing\'s soaring CCTV tower described as one of the most daring pieces of architecture ever attempted and Shanghai\'s 101-storey World Finance Center are also high-profile examples of cutting-edge design. Andreu is designing a colourful archaeological museum in the northern city of Taiyuan and Zaha Hadid the first woman to receive the Pritzker Architecture Prize -- has just finished a 1,800-seat opera house in southern Guangzhou. Renowned British architect Norman Foster, who designed the much-acclaimed Terminal 3 at Beijing\'s international airport, is also building the headquarters for CITIC Bank in the eastern city of Hangzhou. Foreign firms are not the only ones taking advantage of opportunities in China. Homegrown architects are also making their mark at home and abroad. Ma Qingyun, whose firm MADA s.p.a.m. has countless projects across China, was named one of the world\'s most influential designers by Businessweek last year, along with Hadid. Earlier this month, the French Architecture Academy gave its gold medal a top award to Wang Shu, who focuses on sustainable design. \"The architectural arena is changing it\'s leaning towards more intellectual and creative freedom,\" said Andreu. Michael Tunkey, the Shanghai-based partner at international firm Cannon Design, said other countries in Asia were also proving a boon for architects. \"The fact that Chinese salaries have been rocketing over the last couple of years has generated larger opportunities for places like Vietnam and Thailand,\" he said. Nguyen Chi Tam, design director at HighEnd Architecture in Hanoi, said there had been \"more and more\" architect offices opening in Vietnam in recent years both mid-sized firms and global giants. \"With a downturn in Europe, foreign firms have turned to Asia, including Vietnam,\" he said. Tam\'s office is collaborating with famed Italian architect Renzo Piano on a project for a new opera house in Hanoi, while the New York-based Carlos Zapata recently worked on the 68-storey Bitexco Financial Tower in Ho Chi Minh City. But, as in Beijing where much of the old town has been torn down, Hanoi is having trouble preserving its heritage despite a law on conservation enacted in 2001. \"On paper there are still more than 1,000 French villas in Hanoi but in my opinion, there are really only a few hundred that have kept their original colonial style,\" Hoang Dao Kinh, a Hanoi-based architect, told AFP. Preserving the old while embracing the new is a challenge that other Asian nations face too. Singapore, for one, has been relatively successful. To date, more than 7,000 old buildings have been preserved by the city-state\'s national planning authority, adapted into restaurants, offices or homes. But it is also the home of architectural feats such as the $5.5 billion Marina Bay Sands resort that boasts three 55-storey hotel towers linked by a huge sky park 200 metres (656 feet) above the sea. Sustainable engineering is also starting to take hold in Asia. Ciputra World, a business and entertainment complex in Indonesia\'s capital Jakarta, is one such example. The three-trillion-rupiah ($350 million) project aims to reduce energy usage by at least 20 percent compared to a regular building, with double-glazed windows and a sophisticated indoor air system. Back in China, the Pearl River Tower in Guangzhou, due to be completed this year, has been dubbed \"the world\'s greenest skyscraper\". Its structure directs winds to openings where they push turbines that generate the building\'s energy, according to architecture firm SOM, which is working on the project. Tunkey said China is still lagging far behind the United States and Europe in terms of clean technology buildings. \"But if it decides to get in front of the curve, it has got the potential to ramp it up in a way that no other country really can,\" he said. Ma, meanwhile, said China faced a key challenge in the next few years in finding its own architectural path \"that corresponds to Chinese people\'s aesthetic habits and experiences.\"