The commission was the result of a competition, organised by Berlin city authorities, to design two parks. The first, Henriëtte-Herz-Park, was completed last year. But as the second park was to span a rail tunnel, still under construction, and was to function as a building site for new development around Potsdamer Platz, actual construction only started last year.

The Tilla-Durieux Park consists of an expanse of grass, 450 metres long and 30 wide, rotated around its longitudinal axis and transected at just one point. The height, which rises to 4 metres, and the incline of 35º make crossing the park anywhere but through the cut-away a perilous undertaking. The design generated stern resistance, particularly from surrounding residents and property owners. The park would be cold and unwelcoming - to many people a park simply means flowerbeds, trees, promenades and benches - and people opposed the fact that it could be crossed from only one point. Until a year ago these objections threatened the very construction of the park.

Yet Berliners can be glad that the Tilla-Durieux Park is finally finished. The expanse of green offers welcome visual relief amidst the surrounding architectural clamour. The buildings designed by Richard Rogers in particular jostle one another to grab the limelight. But park makes no attempt to dissolve into the surroundings. In fact, the rotated plane turns the expanse of grass into a monumental gesture, into landscape art.

The short-cut at Bernburgertreppe provides a useful connection between Askanischer Platz and Marlene Dietrich Platz. Any other crossing would only have led from somewhere to nowhere. The first design by DS didn't contain any short-cut at all, but the client insisted that it be added. It doesn't detract from the design, however. Quite the opposite, in fact, because the monumentality, emptiness and power of the rotated plane is experienced most keenly from the cut-away.

It may be just an expanse of grass, but the Tilla-Durieux is never dull. Your experience of the green space changes continually as you walk around the park. Nothing is what it seems or what you expect.

The design by DS can be placed within the Dutch tradition of creating a void at the heart of a new district. A space replete with symbolism, the promise of a new beginning, a deliberate tabula rasa. A space where everything is possible, unhindered by what already exists. And it is precisely here in the heart of Berlin - an area totally destroyed by allied bombs in the war and subsequently a barren no-man's-land trapped between East and West Berlin, close to the Wall - it is precisely on this historically charged site that DS has concocted a modern variant of a well-tried Dutch recipe, the promise of the void.