Not so much the millennium's Crystal Palace, more a post-modern hedgehog

The world's largest domed building will be constructed in Britain - if the Millennium Exhibition in London goes ahead as planned.

A huge, domed, tent-like structure will be erected at Greenwich, in south- east London, eclipsing most of Britain's best-known buildings. The size of two Wembley Stadiums or 13 Albert Halls, taller than Nelson's Column, the "Millennium Dome" will be even larger than the Georgia Dome in Atlanta and the Astrodome in Houston, America's two biggest sporting arenas.

On the same day as the contest to develop a national stadium at Wembley hotted up, the Millennium Exhibition organisers unveiled details of what could become, once the year 2000 has passed, the world's largest indoor sporting centre.

Who will own the giant complex by the Thames, once the exhibition has finished, is still open to question. Organisers said yesterday that British Gas owned the 130-acre site on the Greenwich peninsula and that discussions were still taking place between the company and English Partnerships, the government agency charged with regenerating old industrial sites, to clarify the issue.

They stressed that the dome was designed to be taken down if needs be. More than 50 metres high, it will be supported by cabling attached to 12 masts, each 100 metres high. In all, it will provide 102,300 square metres of exhibition space - big enough to park 3,300 London buses.

The idea, said Barry Hartop, the government official now in charge of co-ordinating the project, was "to make a significant statement to the world." Mr Hartop likened it to the Sydney Opera House in scale and with its external piazza and walkways intended to provide a home for entertainers and performance artists, similar to the Pompidou Centre in Paris.

Details of what the dome will actually house remain sketchy. Inside, there will be 12 pavilions, each devoted to a single theme of British life from the past 1,000 years and looking to the future. The overall theme will be "time", with the dome intended to represent a giant clock- face.

Sitting alongside Mr Hartop, representatives from the designers Imagination and architects, the Richard Rogers Partnership, tripped off facts and figures for a project, that if it happens, will dwarf anything ever seen in Britain: 35,000 visitors per hour coming by tube train on the new Jubilee line extension; a capacity of 70,000; more than 2,000 construction jobs; more than 5,000 jobs in the Exhibition proper; specially designed boats shuttling visitors back and forth along the Thames; a new millennium pier; new roads; a strengthened river wall; parking for 500 coaches; 12.5 million visitors during the millennium year.

A one-day visit will not be sufficient, says Mr Hartop, who reckons people will require at least a day-and-a-half to do it justice.

Questions remain, however, over the acceptability of the plans to the Greenwich public - the organisers plan to distribute 120,000 leaflets setting out their plans and to set up a permanent exhibition of scale models - and the final cost.

At present, the project has a budget of pounds 350m, of which pounds 200m is coming from National Lottery funds and pounds 150m is to be provided by private and corporate sponsorship.

But already, sources close to the project have been warning that this figure is too optimistic by far, and that a final cost of pounds 800m or even pounds 1bn looks more likely.

Early reaction from Greenwich was positive. Len Duvall, the leader of Greenwich Council, said: "At last it's landed and it's been worth the wait. It will be an international landmark for the future that will complement historic Greenwich and will mark a new renaissance for London in the 21st century."

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