Loos American Bar
For fans of architecture, the Loos Bar is a must while in Vienna. Adolf Loos, one of the first modern architects in history, is best-known for his infamous Looshaus (1910-12). The building, made for a high-end tailor shop, has a provocatively simple upper facade that outraged the Habsburg royal court living across the street from it.
With the American Bar (1907), hidden on a downtown side street off Kärntner Straße, Loos used rich, expensive fittings: marble, mahogany, alabaster, without superfluous decorations. The cocktail bar is tiny, the impact is striking (lots of mirrors are meant to enlarge the space). That portrait hanging on the wall: he's Peter Altenberg, a close friend of Loos and a famous Viennese coffeehouse poet.
The crowd is heavy on tourists and scoring one of the few precious seats is nearly impossible, but a visit is worth it for a peek at least. Try going during off-hours.