The historic staircase was retained, and now leads to the galleries in the three upper stories. The flexible exhibition galleries in the basement level, together with the upper rooms, add up to altogether 5300 m² of exhibition surface. The Schmela Haus The Schmela Haus was built by Dutch architect Aldo van Eyck (1918–1999), a key representative of structuralist architecture. Inaugurated in 1971, and now under landmarks protection, it was the first building in the Federal German Republic to be erected specifically as a private art gallery. The five-story building, built from gray pumice, is characterized by its interplay of interior and exterior and between its private residential and public exhibition spaces. The building was purchased by the Federal State of North Rhine-Westphalia after being vacated by the gallery. Collection The collection encompasses a singular selection of works from the 20th and 21st centuries. Among the high points are paintings by the German Expressionists, Pablo Picasso, Wassily Kandinsky and Jackson Pollock, and installations by Joseph Beuys and Nam June Paik. Alongside these works, which have long since achieved iconic status, are additional outstanding examples of classical modernism, of American art after 1945, along with major installation works, photographs, and film and video pieces by contemporary artists. Critics have referred to the collection – whose individual works are notable for their outstanding quality – as a "secret National Gallery". The focus of the collection is classical modernism. Stylistically, the works from before 1945 range from Fauvism, Expressionism, Pittura Metafisica, and Cubism to works by members of the Blaue Reiter group, as well as Dada and Surrealism. The collection also includes 100 works by Paul Klee. In 1960, the Federal State of North Rhine-Westphalia earmarked 6 million German Marks for the purchase of 88 paintings, drawings, and color studies on paper by Klee – an ensemble which formed the nucleus of the Kunstsammlung Nordrhein-Westfalen. Although the price tag seemed high at the time, it appears a rare bargain from today's perspective. The works came from a private American collection in Pittsburgh. Among groups of works by individual artists is an ensemble of 12 by Pablo Picasso which encompasses nearly all of the major creative phases of his career. Cubism forms an important focus of the collection, with works in the style by Pablo Picasso, Fernand Léger, Juan Gris, Georges Braque and others. Art after 1945 is represented primarily by circa 40 major pieces