The sweeping curves and contours would not look out of place in a 21st century science park.

But this spectacular new building, designed with the aid of computer technology, is in Sussex alongside some of the oldest properties in Britain.

Bosses at the Weald and Downland Open Air Museum, in Singleton, near Chichester, proudly unveiled their latest exhibit at its official opening yesterday.

The structure, called a downland gridshell, cost £1.8 million to build, is 50 metres long and is constructed from a shaped lattice of curved oak beams which, if laid end-to-end, would stretch more than seven miles.

It has taken a team of boat-builders and specialist woodworkers more than two years to construct.

It encloses an ash floor space of 50 metres by 17 metres, equivalent to almost four tennis courts.

It will house a workshop giving craftsmen space to assemble the wooden frames of other buildings in view of visitors.

The polycarbonate window sheets which run along each side of the roof make the space ideal for craft courses.

Meanwhile the cavernous basement will house the museum's collection of 10,000 tools and artefacts, many of which have never been displayed before.

The building was opened by Sir Neil Cossons, chairman of English Heritage.

Richard Harris, who took over the project following the death of museum director Chris Zeuner in January 2001, said: "Without Chris the gridshell would not have happened. He was the one who pursued a project that seemed quite extraordinary even on paper.

"The downland gridshell is just as much a testament to architectural and building techniques of the early 21st century as the museum's historic buildings are to their own particular time.

"Museums must give accurate and detailed information but they must also inspire visitors and we believe that this building will do that."

The museum specialises in saving historic buildings which had been threatened with the bulldozers to make way for new homes or roads. One farmhouse used to stand close to the entrance to the Channel Tunnel.

More than 45 buildings dating back to the 12th century are now on display in 50 acres of parkland after being taken down by craftsmen who mark every piece and re-erect them rather like a giant jigsaw.

Another 15 buildings are in storage to begin a new lease of life at the museum.

Museum chairman David Tomlinson said: "People will be able to see craftsmen at work while the basement is being used for storage. That means we no longer have to use a barn two miles away."

Among the guests at the opening was Anthea Case, director of the Heritage Lottery Fund, which provided £1.2 million of the £1.5 million cash for the building.

She said: "The gridshell project is not just about protecting the future of historic, timber-framed buildings but also ensuring that endangered heritage skills can be sustained and continue to be passed from generation to generation."