The London 2012 Olympics aquatics centre will be smaller than originally planned in order to save costs.
Culture Secretary Tessa Jowell sent the designer "back to the drawing board" last December as the original £75m budget looked set to double.
The wave-shaped roof will now be 14,000 square feet, which is just over a third of the original 35,000 square feet.
The original capacity of 20,000 seats will remain with 15,000 for the main pool and 5,000 for the diving pool.
Olympics chiefs say the final cost cannot be revealed at the moment due to commercial sensitivities.
London 2012 chairman Sebastian Coe said: "We are on schedule to deliver this landmark venue and as Tessa said last week the budget for the design and construction of all the venues are broadly in line with the out-turn costs prepared.
"This will provide both a functional and beautiful venue for the Games"
"We hope people will understand that we cannot put these figures in to the public domain at this stage as negotiations with design and construction companies are either under way or about to begin."
The aquatics centre is the first major venue to go to the detailed design stage and contractors are already working on the site to prepare the land for construction to start in mid-2008.
The venue is due to be completed in the summer of 2011 and will have two 50-metre pools, one for training and one for competition, plus a diving pool.
During the Olympics and Paralympics it will host all the swimming and diving events apart from water polo, and after the Games it will be converted into a 2,500-seat complex with the potential to add in a further 1,000 temporary seats for European events.
Jowell said in a statement that the design, by architect Zaha Hadid, was "inspirational".
She said: "This will provide both a functional and beautiful venue for the Games, a legacy for the local community and will, no doubt, in time become a distinctive landmark in the Olympic Park."
London mayor Ken Livingstone added: "Zaha and her team have carefully recrafted their original concept and produced a truly world class aquatics centre design."