BEIJING, Dec. 24 (Xinhuanet) -- Construction of the National Stadium and the National Swimming center, two of the main venues for the 2008 Olympic Games, started on Wednesday, launching a three-year building project for the games.

With an investment of 3 billion yuan (about 360 million US dollars), the National Stadium, known as "bird's nest" because of its giant lattice-work structure of irregularly angled metal girders, will be the centerpiece of the 2008 Games.

The 80,000-seat National Stadium, located in the south of the Olympic Green, will host the opening and closing ceremonies as well as track-and-field events during the 2008 Olympics.

The National Swimming Center, being located in the Olympic Green as one of the landmark architectures, covers a floor space of 70,000 square meters.

With 17,000 seats - 6,000 permanent ones and 11,000 temporary ones, the swimming center will host swimming, diving, water polo and synchronized swimming events during the 2008 Games.

Apart from the National Stadium and the Swimming Center, the first group of venues to be built will also include the Beijing Shooting Range and the Laoshan Velodrome.

Bids for other Olympic projects, including the Olympic park on the northern edge of the city, are also under way.

Beijing promised to finish construction of its sporting facilities for the 2008 Games at least a year ahead of time so test events could be held during 2007.