'It's absolutely not a white cube,' says Belgian architect Paul Robbrecht about the new pavilion his Ghent-based practice Robbrecht and Daem (also responsible for the renovation and extension of London's Whitechapel Gallery) has designed for the Middelheim open-air sculpture museum in Antwerp. Pointing out the exposed columns and 'knots' where the beams have been welded into the green steel structure, he adds: 'What we really wanted to do was make a building that shows how it is built, that shows the tectonics of construction.'

Het Huis (house or home in Dutch) has been purposely laid out at diagonal angles to the straight paths of the formal gardens it was built in so that it looks 'woven into the surrounding landscape'. This is a theme Robbrecht refers to repeatedly, revealing that one of his greatest sources of inspiration was 19th century German architect and art historian Gottfried Semper's notions of the 'textile origins of building'.

The brief for the semi-open structure was straightforward. 'It was for a pavilion that would have real contact with nature, with the landscape around it, a place where smaller or fragile works of art could be shown, or works that needed a more framed setting,' says Robbrecht. The colourful but unsettling glossy ceramic heads and urns of German artist Thomas Schütte displayed here were created especially for the pavilion's inauguration and contrast ingeniously with the smooth concrete floors, geometric lines and angles of the roof and the special 'topography' of the ceiling, which 'looks as if it's moving'.

The pavilion represents nature in architecture, says Robbrecht. Two trees have been planted at opposite ends of the space and steel lattice-patterned screens (which can be pulled across the four openings to close the pavilion at night) create extraordinary dappled effects as if light is coming through the branches of a tree. 'You could almost think it's a roof of leaves above you,' Robbrect says excitedly.

After touring the 200-plus sculptures (including new site-specific works by Ai Weiwei, Philippe Van Snick and Roman Signer) in the freshly extended 75-acre park and revamped museum, visitors will find Robbrecht and Daem's angular steel-and-concrete 'house' a place of extraordinary peace, intimacy and poetry.