Tate Modern shows off new pyramid tower

Tate Modern has unveiled its new extension, a pyramid-like tower housing cavernous gallery spaces, ahead of its official opening.

The 200ft (65m) structure, boasting panoramic views of London, is part of a £260m revamp of the world-famous art museum.

It is being billed as the UK's most important new cultural building since the British Library.

More than half of the solo displays are dedicated to women artists.

At Tuesday's launch event, Frances Morris, Tate Modern's new director, promised a weekend of "discovery and celebration" when the new building opens to the public on Friday.

"As we have been building the new Tate Modern, the curators... have been building the collection," she said. "You will find more international art, more art by women and great new installations."

She added the representation of women artists had "substantially increased".

"There was a huge deficit in our collecting prior to 2000 - when we opened 17% of the art on display was by women.

"Now 50% of the solo rooms are works by women such as Phyllida Barlow and Louise Bourgeois."

A look inside the 10-storey Switch House

The new 10-storey building, known as the Switch House, includes three new gallery levels and a panoramic roof terrace.

It allows 60% more artworks from the Tate collection to go on show.

Tate director Sir Nicholas Serota expressed delight that the building work had been completed during a period of recession.

"Our aim is to be local, global, to have relationships with communities close to us and those across the world," he said.

The project was undertaken by architects Herzog & de Meuron, who transformed the derelict Bankside Power Station into Tate Modern in 2000.

The new Switch House rises almost 65 metres to the south of Tate Modern's huge Turbine Hall.

The windows and the viewing terrace appear as "cuts" in the surface which is clad with 336,000 bricks that mirror the look of the original building.

The tower is built above the former power station's subterranean oil tanks which were converted into performance spaces in time for the 2012 Olympics.

Analysis by BBC arts editor Will Gompertz

The new Tate Modern is bold, both in its physical form and its curatorial hang.

The original building played a part in transforming the public's opinion of modern art; the contents of the new building is asking audiences to take an even greater leap of faith.

It's filled with art they've probably never seen from artists they've probably never heard of - and there's hardly a painting to be found.

It's a bold move by the Tate, but, in my view, an entirely appropriate one.

The old story of modern art which is dominated by white western males is being turned on its head with a new narrative that shows how artists of all types from across the globe have contributed and are contributing to the story of modern contemporary art.

Yes, there are a few misses, but they're far outweighed by the hits - and the way the works have been hung together in thematic galleries is both intelligent and illuminating.

Plans for the project were initially approved in 2007 because the gallery space, designed for two million visitors each year, was attracting five million. Building work began in 2010.

Tate chairman Lord Browne described the gallery's £260m revamp as the largest cultural fundraising campaign ever launched in the UK.

"A building that was once London's beating heart is now its cultural cathedral," he said at Tuesday's launch.

Significant donations have come from the government (£50m), the Greater London Authority, Southwark Council and private foundations and individuals.

Sadiq Khan, the new mayor of London, said the new Tate Modern would add to the capital's "huge cultural pull".

Tree sculpture

The Switch House tower includes galleries, a restaurant and a viewing level

The Tate Modern relaunch is accompanied by a complete rehang of the gallery's artworks which will showcase more than 300 artists from about 50 countries.

Works by Mark Rothko, Agnes Martin and Joseph Beuys are joined by new acquisitions by Meschac Gaba, Sheela Gowda and Cildo Meireles.

A huge sculpture of a tree by Chinese artist Ai Weiwei stands in the centre of the Turbine Hall.

Some 3,000 school children from across the UK will be the first members of the public to see the new Tate Modern at a special preview on Thursday.

Later this year Tate will launch Tate Exchange, an "open experiment" occupying an entire floor of the new Switch House building, that will enable 50 invited organisations from the across the UK to display their work.