From the architects site:
Nature arranged on many levels provides both an extension to existing nature and an outstanding symbol of its artificiality. It provides multi-level public space as an extension to existing public spaces. And even by arranging existing programs on many levels it provides yet more extra space, at ground level, for visibility and accessibility, for the unexpected, for “nature.” Dividing up the space in the Dutch entry and arranging it on multiple levels surrounds the building with spatial events and other cultural manifestations. The building becomes a monumental multi-level park. It takes on the character of a happening.