Located just across the river from the main gallery building, the Serpentine Sackler Gallery occupies a 200-year-old former gunpowder store. Zaha Hadid Architects renovated the old brick building to create new gallery spaces, then added a curving cafe and events space that extends from one side.
The new tensile structure is built from a glass-fibre textile, forming a free-flowing white canopy that appears to grow organically from the original brickwork of the single-storey gallery building.
It stretches down to meet the ground at three points around the perimeter and is outlined by a frameless glass wall that curves around the inside.
Five tapered steel columns support the roof and frame oval skylights, while built-in furniture echoes the shapes of the structure.
"The extension has been designed to to complement the calm and solid classical building with a light, transparent, dynamic and distinctly contemporary space of the twenty-first century," explain the architects. "The synthesis of old and new is thus a synthesis of contrasts."
For the original building, the architects added a new roof that sits between the original facade and the outer enclosure walls, creating a pair of rectangular galleries in the old gunpowder stores and a perimeter exhibition space in the former courtyards.
A series of skylights allow the space to be naturally lit, but feature retractable blinds to darken it when necessary.
The Serpentine Sackler Gallery is Zaha Hadid's first permanent tensile structure in the UK and follows the studio's Lilas installation at the gallery in 2007 and pavilion in 2000.
The gallery opens with an exhibition from Argentinian artist Adrián Villar Rojas.
This year's Serpentine Gallery pavilion by Japanese architect Sou Fujimoto is a cloud-like grid of steel poles and remains open in Kensington Gardens until 20 October.
Zaha Hadid has also recently revealed the first in a chain of boutiques for American shoe designer Stuart Weitzman and plans for an 11-storey apartment block that will be constructed beside New York's popular High Line park, while her forthcoming National Stadium of Japan is now set to become the main sporting venue for the 2020 Olympic and Paralympic games.