Four supporting walls running from north to south and standing 7m apart define the plan of the building. Movable partitioning walls create about 19 rectangular, ground floor rooms with an exhibition area of 2,700 m².

The unusual thing about the architecture is that it unites two basic yet contrasting themes: solid, lengthy walls and a light glass roof 'floating' overhead. The complex roof construction is spread over the galleries like a 4,000 m² canopy. 864 louvered screens in saw-tooth formation afford protection from the sun.

The building opens onto the park via a conservatory and thereby establishes a direct relationship between indoors and outdoors. Matching the hues of Basle Cathedral's sandstone, all the external walls are clad with red porphyry stone from Patagonia.