What makes Paris look like Paris? Carl Doersch, a Ph.D. student in machine learning, and his CMU colleagues developed visual data mining software that can detect sometimes subtle features, such as street signs, streetlamps and balcony railings, that give cities a distinctive look. It was a hit at SIGGRAPH in 2012 and is on the cover of December's Communications of the ACM. Read the research article and watch the accompanying video. In a technical perspective, Cornell University's Noah Snavely describes automatically detecting a place's visual signature as "magical."