Foursquare is a great way to let friends know what we're up to, or check reviews of a local restaurant. With the popularity of Foursquare, and the numerous 'check-ins' by users, it has a pretty good idea of what people are doing at different times of the day. Recently, Foursquare decided to use the data users give them to visualize how we move about in some major cities. They took check-in data over the period of a year, and plotted it over a map, updating it by hour of day. The result is quite fascinating, especially if you live in one of these cities.