The Künstlerhaus was built between 1865 and 1868 as the house of the Viennese artists’ association — Renaissance Revival, with a sandstone façade and a green copper roof that most visitors walk past without looking up. The Salon Karlsplatz sits inside it: parquet floors, panelled walls, painted portraits below a gilded ceiling, and a grand piano. A room for eighty people rather than a thousand, which is why the concert sounds the way it does.