The data created from tagging tweets with their location can be used in a number of interesting ways, and Twitter's Visual Insights team has recently used that information to create some terrific visualizations of cities across the globe. Every single dot on the map represents a tweet, and according to Twitter there are billions of them, dating all the way back to 2009. The result is a series of strangely beautiful maps that show just where people are tweeting from. Check out the entire Flickr gallery to see everywhere from Seoul and Sao Paulo to Seattle and Sydney.