Due in part to its privileged location across from St. Stephen’s Cathedral, Hans Hollein’s Haas Haus was highly controversial when it was built in 1990. The building and its curved façade are centred around the historical quadrant corner of the old Roman castrum. This architectural ensemble on Stock-im-Eisen-Platz and Stephansplatz stands as a statement of our times, yet it still fits in largely due to its mirrored glass façade.