OLYMPIC GAMES: Plain but powerful, and offering a post-Games legacy, is how the designer describes London's flagship venue for the 2012 Olympics.

Designs for London's main Olympic stadium were unveiled yesterday as organisers claimed the arena would set new standards for major stadium construction and prove a practical, affordable legacy to the England capital after the Games. They did not, however, rule out seeking contingency funding to help pay for the project if the estimated 712 million budget were exceeded.

An artist's impression of the plain, Coliseum-style bowl, which features a mix of temporary and permanent seats, was met with silence when it was unveiled to officials and dignitaries on the Olympic Park site yesterday morning, but while the stadium lacked flamboyant touches, organisers acclaimed a design focused on the practicalities of the post-Games legacy.

The 80,000-seater arena, which will host the opening and closing ceremonies and the track and field events in 2012, includes 55,000 temporary seats and will be reduced to a permanent capacity of 25,000 in 2013.

The design is driven by a commitment made during London's bid to leave a world-class athletics legacy in the capital rather than a succession of grandiose white elephants.

The contrast with the spectacular "bird's nest" stadium taking shape in Beijing for next summer's Olympics could not be greater, but the architect Rod Sheard, of HOK Sport, was unapologetic.

"This is not a stadium that's going to be screaming from the rooftops that it's bigger and more spectacular. This is just a cleverer building. This is a cleverer solution," he said.

"Olympic stadiums tended to get a reputation as white elephants so we had to come up with some different answers. While it does not have a spectacular arch like (Wembley) in north-west London, it is an unbelievably complex stadium that is resolved in a simple and elegant way."

The stadium will be built on an island at the conjunction of the river Lee and the City Mill river. The track and playing field and the bulk of the 25,000 permanent seats will be in a sunken bowl.

The temporary seating will be built on top, its steel structure concealed behind a material "wrap" likely to be decorated with flags of competing nations, or variations on the controversial logo design.

The cable-supported roof, which will cover only two-thirds of the seats, will be suspended from a steel frame resembling an upturned crown.

Sheard, whose design credits include the new Wembley stadium, the main grandstand at Ascot and the planned Centre Court roof at Wimbledon, said the design was innovative and would provide an intimate, powerful atmosphere.

"We've ended up with a very tight, very compelling bowl," he said. "The atmosphere inside this bowl, we think, will be pretty special."

To cut costs and make the demounting (rearranging) of the stadium more straightforward the bulk of the services usually found inside - catering, bars, toilets and merchandise stalls - will be located in "pods" on the concourse outside the stadium.

"It's the 21st century and it's time we started doing things differently," said Sheard. "The agenda laid down by Seb (Coe) and his team demanded that we do this one differently."

John Armitt, chairman of the Olympic Delivery Authority (ODA), described the design as "inspirational", but indicated that costs could rise.

"We have an estimated price today of £496 million (€712 million)," he said.

"In terms of our ability to work within it, £500 million (€718 million) is a lot of money in anybody's terms and we're determined to work within it, but if for any reason whatsoever there is a requirement for some extra then we have a contingency within the scheme covering this and we may have to use some of that, but that is not the plan."

Questions also remain as to how the 25,000-seater stadium will be funded in post-Games mode. The stadium will be used for community sport and education and host international athletics meetings, including world and European championships, but track and field is not profitable enough to sustain the complex.

Armitt conceded yesterday the ODA had not yet identified an anchor tenant from professional sport; Saracens and Wasps rugby clubs and Leyton Orient football club are known to have reservations about moving to the stadium.

London's mayor, Ken Livingstone, was confident a tenant would be found soon.

"No one in their right mind was going to sign up for a facility before they had seen the designs, but now we have the plans I'm confident that we will move very quickly," he said.

Main features of the design

• a sunken bowl built into the ground for the field of play and lower permanent seating, designed to bring spectators close to the action

• 25,000 permanent seats, 55,000 demountable seats

• a cable-supported roof that will stretch 28 metres the whole way around the stadium, providing cover for two-thirds of spectators

• a fabric curtain wrapped around the stadium structure, acting as additional protection and shelter for spectators

• facilities such as catering and merchandising grouped into self-contained "pods"

During The Games

The Olympic Stadium will seat 80,000 and will be the main venue for the Olympic and Paralympic Games. All Athletics events will take place in the Stadium as well as the Opening and Closing Ceremonies.

After the Games

After the Games the Stadium will be converted to a 25,000 seat Athletics stadium with a range of facilities available for elite competitors and the local community.