'Stingray' roof lowered onto 2012 centrepiece

With its dazzling undulating design and prominent positioning at the entrance to the Olympic Park, ministers hope that the London Aquatics Centre will be the architectural jewel in the capital's crown come 2012. Today they breathed a collective sigh of relief as the building's 2,800 tonne "stingray" roof was finally lowered into position after eight months of painstaking preparations.

Designed by the Iraqi-born British architect Zaha Hadid – who for much of her career had a reputation for creating astonishing building designs that frequently won architectural competitions but often never made it off the drawing board - the aquatics centre will be the first building to greet visitors to the Olympic Park in east London. It is already being hailed by critics as the most architecturally stunning centrepiece of the Games.

But building the centre is no mean feat and today's completion of the roof was hailed by Olympics chiefs as the most structurally complicated part of the Games.

Construction work on the centre began two months ahead of schedule in March this year and has almost entirely revolved around getting the roof into place. Despite its astonishing weight, the wave-like roof is only being supported at three points, two enormous concrete pillars at the north end and a five metre thick concrete wall at the southern end.

Before placing the roof onto the pillars and wall, structural engineers had to lift a 70 tonne steel truss onto the concrete wall and connect that to a series of ten further trusses that stretch to the two pillars on the other side. The trusses were assembled on site at a height of 20 metres using steel scaffolding to make it easier to lift the full roof onto its joints on the concrete supports. After carefully removing the scaffolding, engineers allowed the roof to slide a final 20cm onto its joints on the southern wall which will allow the building to stretch, twist and contract with the weather.

Olympic chiefs hope to complete the building by 2011 and once opened it will be able to seat 17,500 spectators during the Games. After the Olympics the capacity of the stadium will be reduced to 2,500 but the two Olympic sized swimming pools will remain, giving east London the country's best equipped swimming facilities.

Although the project has been praised for its architectural style – former mayor Ken Linvingstone credited Hadid with helping to swing the Olympics London's way – critics have winced at its spiralling costs which have risen from £72m to more than £250m.

Hadid, who was born in Baghdad and moved to Britain in the 1970s, was not in Stratford today to see the roof's completion. Instead she was celebrating the completion of another one her characteristically striking creations, the MAXXI art museum in Rome which officially opens tomorrow. Italy's latest art museum is as modern looking as the art it will soon hold and comprises a series of interwoven concrete buildings layered on top of each other like a pile of Scalextric track.

Engineers will now turn their attention to excavating the two 50m swimming pools and the 25m diving pool. The roof itself will be clad in aluminium.