The design for the 2012 Olympic stadium, based on a sunken bowl, has been unveiled.
Olympic organising committee chairman Lord Coe described it as a "stadium for a completely new era that will be inspiring and have a lasting legacy".
It has 25,000 permanent seats sunken into the bottom, with a layer of 55,000 temporary seats above and a roof that will cover two-thirds of all spectators.
Outside the stadium will be pods filled with facilities for spectators, such as food stalls.
Key to the design of the £496 million venue in Stratford, east London, is that it must shrink from an 80,000-seat capacity venue during the Games to one of 25,000 seats afterwards.
It will then become a multipurpose venue used for athletics and other sporting and community events, but no anchor tenant has yet been found.
Original cost estimates did not include VAT and inflation.
John Armitt, chair of the Olympic Delivery Authority, said: "Nearly £500 million is a lot of money in anyone's terms but it is the budget and we are determined to work within that.
"If there is a requirement for any extra, we have a contingency within the scheme covering this as a whole and we will use some of that, but that is not the plan.
