It doesn't matter how many times I look at this image: I still find it stunning. I have a 3-foot by 3-foot version printed on canvas that hangs on my wall.

What exactly is it, you may ask? It's San Francisco, mapped by photo locations from Flickr and Picasa search APIs and then plotted on OpenStreetMap. Those posting photos in a given city for more than a month are considered local (blue); those posting in the given city for less than a month who appear to be residents of another city based on their posting are considered tourists (red). Yellow designates those not fitting into either category (likely but not conclusively tourists). Lines connect places where the same person took two pictures within ten minutes of each other.

It's simultaneous art and information discovery. The expected places are red: Golden Gate, Alcatrez, Fisherman's Wharf. But there are some places I hadn't realized were so frequented by tourists until I studied this infographic: twin peaks, AT&T stadium, Berkeley. Makes sense, just not something I would have known before seeing the data.

This piece is part of a collection (currently made up of 135 cities) called Locals and Tourists by Eric Fischer. Take a look, find your favorite city, and see what you can learn!