Unveiled: this summer's Serpentine Pavilion

Imagine a giant Pandora’s Box made from a wooden frame, covered with linen that has been coated with a mixture of waterproof black paste and sand: hidden inside is a big surprise. Now, park the box in the middle of the Serpentine Gardens, Kensington, in July.

Hey presto, welcome to this year’s Serpentine Pavilion which, it has just been announced, will be designed by major international award-winning Swiss architect Peter Zumthor. The pavilion will open to the public in July.

You will enter this mysterious, highly theatrical structure (whose final shape is still on the drawing board) and walk through the gloom to the surprise: a large internal, skylit garden, that you can wander and sit around, and contemplate. This internal ‘garden within a garden’ will be designed by Dutch garden designer Piet Oudolf, whose innovative work in mainland Europe uses both bold structure and strong colour.

This will be the 11th Serpentine Gallery Pavilion. In some senses it will be both the most modest and the most ambitious; for with its deliberate use of wood and ‘scrim’ (a stiff linen used in the theatre) it returns to the true ‘pavilion’ idea of a very temporary structure - just as set designers, since the Middle Ages, have conjured miracles of delight and deception with the same cheap materials.

Every pavilion is put up very fast on the lawn in front of the Serpentine Gallery. The architect only gets three months to design and build it, and it only lasts for three months. But during that time, thousands of Londoners visit what has become a big draw for the capital, while the pavilion itself hosts talks and events during its brief summer lifespan. This one is a sort of Big Top with flowers.

The programme has been so successful since it began in 2000 that the architectural bar seems to raise every year. Only architects who have not yet built in England are considered, and the roster now includes Jean Nouvel, Frank Gehry, Daniel Libeskind and Zaha Hadid (who was the first). Some of the pavilions have had several storeys, while Libeskind’s was famously made out of solid aluminium whose flashing in the sun famously distracted unwary cab drivers.

To date, some of Zumthor’s buildings, often of apparently simple form, have contained inner secrets. His Bruder Klaus Chapel in Germany, that won Japan’s equivalent of the Stirling Prize (the Praemium Imperiale) in 2008, is also an ostensibly simple box structure, with a triangular door. But the space inside, made by casting concrete around 120 trees that were then burned away, is magically top-lit by a beautiful, wavy-edged opening.

This sense of mystery and wonder, both of sensation and material; of almost childlike delight at finding delicious secrets inside a box - a kind of architectural Kinder Surprise - has become one of Zumthor’s trademarks. As the Serpentine Pavilion enters its second decade, Zumthor is a perfect choice.