Tate Modern shows off new pyramid tower

Tate Modern's new extension, a pyramid-like tower that transforms London's skyline, has been been unveiled ahead of its official opening, the BBC reports.

The tower, billed as Britain's most important new cultural building in two decades, is part of a £260m revamp at the famous modern art museum.

The 10-storey building includes three new gallery levels and a panoramic roof terrace.

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

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

The new building, known as the 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.

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.

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

Tate bosses have previously described the gallery's £260m revamp as "one of the largest cultural fundraising campaigns ever launched".

Significant donations have come from the government, the Greater London Authority, Southwark Council and private foundations and individuals.

In 2006, it was projected the new building would cost £215m at 2012 prices.

The Tate Modern relaunch will be 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 will be joined by new acquisitions by Meschac Gaba, Sheela Gowda and Cildo Meireles.

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

The displays in the new Switch House will explore how art became "active" - starting in the 1960s - with works including Roni Horn's four-tonne cube of pink glass and David Medalla's bubble fountains.

The new Tate Modern opens to the public on Friday.