You know the architecture of Paris when you see it. But what makes Parisian architecture distinctive? What visual elements come together to produce a particular urban landscape? Five scholars from Carnegie Mellon and the École normale supérieure are trying to give precise answers to those questions. And they're taking a novel approach. They're running a large repository of geotagged imagery from Google Street View through a proprietary algorithm and then identifying the distinctive architectural elements for each locale -- the street signs, windows, balconies that make a city unique. Their experiment (all summed up in a short abstract here) covers Paris, London, Prague, Barcelona, Milan, New York, Boston, Philadelphia, San Francisco, San Paulo, Mexico City, and Tokyo.