Return of the dome

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London's most famous white elephant is being reborn as an American-style entertainment behemoth complete with cinema, bars, clubs and an arena that can range from 3500 seats to 23,000.

After six years of eerie silence, the Millennium Dome is ringing to the sound of frenzied construction activity again. Only it's not called the Millennium Dome any more: the financial pull of corporate sponsorship has led to it being reborn as The O2 - a name gloriously free from negative associations (depending on how you feel about a national landmark being named after a mobile phone company).

The dome may have been rebranded but its American developer, Anschutz Entertainment Group, is not entirely breaking with the past. As with its former incarnation, the plan is for the vast structure on the Greenwich peninsula to become a popular entertainment venue, this time with a 23,000-seat arena at its heart. Sceptics may not be heartened to learn that this is based on an American concept of entertainment complexes where the punters schlep to large "destination venues" in downtown districts. The £500m redevelopment will follow this model by providing a wide choice of bars, restaurants, a cinema and possibly a casino and the arena. However, whereas its American cousins are primarily designed for sports events, AEG wanted the arena to be primarily for concerts but flexible enough to host sporting events. This means it needs to be capable of hosting 23,000-seat spectacles and also more intimate 3500-seat events without appearing empty.

This presented architect HOK Sport with a considerable challenge. "This has to be completely adaptable so it can accommodate motor sports one day and Bob the Builder the next," says Nicholas Reynolds, associate principal architect on the project. While contractor Sir Robert McAlpine and engineer Buro Happold have had the task of working out how to build an arena inside an existing building (see "Raising the roof within a roof", below right), Reynolds has been concentrating on ensuring the space is as flexible as possible. The terracing is the first element in this strategy. "The lower bowl is very much the machine of the building," says Reynolds. "The terracing can respond and adapt to whatever event is being staged, so everyone can get a good view."

Visualisations showing the entertainment district outside the arena.

The exhibition centre, encased in an Eden Centre-style bubble

The lower bowl has seating that can be retracted at the sides and added at the ends so the floor can be configured for gymnastics. Moveable seat terraces can be extended at each of the ends to allow for a band to perform in the centre, or can be removed at one end, adding seats to the floor if a concert demands a stage at one end of the arena.

The seating bowl has been divided into two main public tiers and two tiers of suites with the upper tier used for large events only. This allows smaller events to retain some sense of intimacy.

The second key element to the building's flexibility is the service yard. This is housed inside the dome in an area partially occupied by the air vent to the Blackwall Tunnel, which runs below it. "The service yard is designed to work extremely hard and can accommodate 18 articulated lorries containing everything needed to transform the building overnight from, say, a rock concert venue to an ice hockey stadium," says Reynolds. "It has the space to accommodate all the people and activity needed to engineer the changeover in as short as time as possible, and has the advantage of being covered as well."

Obviously, the final factor in making The O2 a success is ensuring that there is enough going on to attract high-spending punters. AEG will inevitably be very aware of this as only half of the predicted number of people visited the original dome. So there's plenty of choice. If they don't want to mix with hoi polloi in the standard seats, they can luxuriate in one of the 96 suites, which are arranged over two levels and are much bigger than football boxes. There's also a restaurant where people can watch events while they dine, as well as more restaurants and other attractions. Construction is coming on well and, in June 2007, the public will be able to judge whether the dome is finally living up to its promise.

What’s going inside the dome

The arena takes up the centre of the O2 but the dome does, of course, cover a vast space. The service yard has a structural frame above
it ready for a casino if this gets permission. This depends on the panel advising the secretary of state of the Department for Culture, Media and Sport – they will decide at the end of the year on the location of new casinos.

Sir Robert McAlpine also has a second contract to build a 32,500 m2 entertainment district in the space between the arena and
the edge of the dome. This will include a 2200-capacity music club, a 6000-seat exhibition centre housed inside an Eden Project-style bubble and an 11-screen cinema. The area will also house bars, restaurants and leisure facilities. Even then, there is a section of empty space, amounting to about one-quarter of the area between the arena and the edge of the dome to the north-west. Details for this area have not been finalised.

Raising the roof within a roof

Stepping on site at The O2 arena is a strange experience. You are, after all, witnessing a building being constructed inside a completed building. It’s the scale of the thing that is so striking. There is all the paraphernalia associated with any big construction project – with the exception of tower cranes. There are diggers, dumper trucks, mounds of earth and busy workers. Eight completed cores are arranged in a giant circle rather like an outsized Stonehenge. Below this, on the ground, is another large domed structure. This is the roof of the new arena.
“The design of the roof and how you build it has driven the whole project,” says Ken Jones, associate director at engineer Buro Happold. Because there is only 5 m clearance between the arena roof and the dome fabric, there is no room for cranes above it. It has to be built on the ground as a unit, then jacked 40 m up into its final position.

And this is no ordinary roof. Its structure is 11 m deep at its apex. This is primarily because its 135 m span necessitates very deep trusses. This space also houses the kit needed for the arena – up to 100 tonnes of concert rigging including lighting, sound equipment and a giant scoreboard that will be lowered for sporting events. There are huge ducts for the environmental control of the stadium and sophisticated acoustic cladding.

“It has to provide excellent acoustics for concerts and also stop noise breaking in and out of the arena. It should be Europe’s leading arena from the acoustic point of view,” says Jones.

Surprisingly, given its location, the roof is a watertight cap. Does this mean the dome will be taken down around the arena as it nears the
end of its 20-year design life? Not according to Reynolds. He says it cost very little to make the building watertight, and that it will probably last longer than its design life. Furthermore, the arena has been designed to be integral to the dome – for example, the public concourses aren’t enclosed within internal walls but are rather like giant balconies overlooking the rest of the dome.

Contractor Sir Robert McAlpine wants to get much of the roof as possible finished before jacking it up. The reason is safety: “When it’s up, people shouldn’t have to go up there to do any work,” says Peter Carruthers, McAlpine’s project director.

From 6 March the 4500-tonne structure will be jacked into an intermediate position 10 m above the ground. Computer-controlled strand jacks installed in the roof will inch the roof up the thick cables, or “strands”, attached to the tops of the eight cores. This will enable work to begin on building the arena on the ground while the roof is finished off. The roof will be jacked into its final position by May.

Carruthers won’t be able to relax after the roof is done. “It takes a year to do the roof, so we have less than a year to do everything else, so we will have to go like hell,” he says. Everything else includes the structural frame, the cladding and the contents. Carruthers has to ensure nothing causes a delay. “Everything that needs to be procured is procured, everything that needs to be fabricated is being done so it’s all available when we come to build it,” he says. “Up to now it’s gone very well and we are ahead of programme. But the difficult bit is still to come …”