Kazuyo Sejima and Ryue Nishizawa’s vision for Sydney’s Art Gallery of New South Wales will be realised after SANAA architects were named winners of the contest to design the AU$450m (US$344m, €315.6m, £225.2m) revamp of the facility and surrounding area.

As part of the expansion, the existing building will become “a global cultural landmark” amid plans to double the size of the 23,000sq m (247,500sq ft) gallery.

SANAA’s design incorporates the gallery’s surrounding topography and climate, with exterior design featuring cascading platforms of sandstone and glass connecting the gallery to its surroundings – including the botanic gardens on which it will incorporate a new wing.

The expansion and redevelopment will include new educational facilities, space for live performances, open exhibition space and the re-introduction of natural light to the gallery’s original 19th century exhibition spaces.

SANAA And the Art Gallery of New South Wales will now collaborate to finalise design plans. The contest was initially opened up to 12 invited architecture firms, before being narrowed down to the final five. The existing Art Gallery NSW building dates back to 1896 and attracts 1.3 million visitors annually. If plans go according to schedule, the gallery will open in 2021 ahead of the institution’s 150th anniversary.