The Whitechapel Gallery today unveiled its "ambitious" expansion following a £13.5 million campaign.
The Heritage Lottery Fund-supported project, due to open in April 2009, unifies the gallery with the Passmore Edwards Library next door, increasing gallery space by 78%.
Designed by Belgian architects Robbrecht en Daem, the venue is billed as one of the most exciting new cultural buildings in Europe.
The gallery, which is over a century old, is affectionately known as "the artists' gallery" and gave a platform to now famous figures such as Gilbert and George and Freud earlier in their careers.
It also gave UK premieres to international names such as Pablo Picasso, Frida Kahlo and Jackson Pollock.
The gallery and library are paired landmarks on Whitechapel High Street in east London, two of many buildings founded in the area by 19th century philanthropists.
As a central focus for thinkers and artists in British modernism, the library became known as the "university of the ghetto".
Included in the expanded building are new galleries dedicated to presenting collections and new commissions; a permanent gallery and research room for the gallery's historic archive and an education and research tower including creative studios. They have been designed by the architects in collaboration with artist Rachel Whiteread.
The new project also boasts a weather vane based on Erasmus, designed by artist Rodney Graham.
The original exhibition spaces in the gallery will be the site for a major exhibition of German sculptress Isa Genzken, the first major retrospective of her work, until June 2009.
Genzken combines traditional materials such as plaster and concrete with everyday materials.
Previous projects include her own architectural proposal for Ground Zero.
The Whitechapel Gallery said it would provide "unprecedented" public access to important art collections with an inaugural display of rarely seen works from the British Council collection.
Iwona Blazwick, director of the gallery, said it was the venue's mission to bring works which had been hidden away back into the public arena.
She said the venue would shift its focus to becoming a destination with a much broader programme where "there will always be something new".
The Bloomberg Commission will give a new platform to an annual art commission.
Ms Blazwick admitted that creating a single installation could be a "big risk".
The Commission will launch with a site specific artwork by Goshka Macuga, who was inspired by Picasso's Guernica while visiting the gallery in 1939 on its first and only trip to the UK.
Macuga will trace the significance of the great Spanish civil war painting.
Forming the centrepiece of the installation will be a life-size tapestry replica of the work.
Macuga has been nominated for this year's Turner Prize.
The gallery's 100-year-old archive will be brought to life with displays of documents and artists' letters.
Ms Blazwick said: "This century-old institution is the artists' gallery for everyone.
"The exciting expansion enables the Whitechapel Gallery to open all year round so there will always be something free to see.
"The gallery will become a major cultural resource and a destination for the arts."
Two years ago a painting by Damien Hirst sold for £450,000 as part of an auction of more than 60 works to raise money for the gallery.
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