LONDON (REUTERS) - Britain's Tate Modern unveils a new pyramid-like tower extension, significantly adding to the famed London art gallery's exhibition space.

The 10-storey high Switch House, which increases the size of the gallery in a former power station on the River Thames by 60 per cent, is part of a 260 million pound (S$500 million) revamp project.

On Tuesday (June 14), the press got a preview of the new wing, which officials at the Tate Modern are calling "Britain's most important new cultural building for almost 20 years."

The gallery has re-hung some 800 works by more than 300 artists.

New acquisitions such as 1930s photography by Lionel Wendt and 1960s sculpture by Lebanon's Saloua Raouda Choucair add to works by the likes of Pablo Picasso and Henri Mattisse.

Half of the solo displays are dedicated to female artists.

Contemporary works on display include a model of the ancient Algerian city of Ghardaia made entirely of couscous by Kader Attia, a room full of human hair and car bumpers by Indian artist Sheela Gowda as well as a tower of 800 radios by Brazil's Cildo Meireles.

Like the main gallery, which opened in 2000 and attracts 5 million visitors a year, the 65-metre high extension was designed by Swiss architects Herzog & de Meuron. The building is clad in a lattice of 336,000 bricks in a nod to the power station's brickwork.

It also boasts a public viewing level offering 360 degree panoramic views of the British capital.

The 'New Tate Modern' will open to the public on Friday (June 17).