The original building was designed by Bakema and Van den Broek in 1958–62. Their ponderous brutalism resounds through the massive walls of the extension, where the trees on the site have left their imprint—literally. A pair of majestic trees had to be felled to make room for the building, but these were molded and cast in silicone to create a relief by Swedish artist Lars Bergström. The memory of the trees has turned into photorealistic, three-dimensional cavities in the deep concrete wall.

Its location behind the main building allows the addition to fall in with the pattern of the site. At the same time, the placement above the glass boxes of the entrance and café give the concrete tube a levity that is enhanced by its dramatic cantilever toward the lake. Seven meters high and seven wide, the long and narrow art gallery is designed for temporary sculpture exhibitions. Bold daylighting through several large openings in different directions varies the character of the eighty-five-meter-long space and links it to the sculpture park outside.

A new catwalk over the refurbished plaza points the way directly to the new entrance.