What happens when you plot billions of geotagged Tweets on a map? You can see the arteries of the world. Here's Europe:
According to creator Miguel Rios (Engineering Manager, Data Visualization at Twitter), the dots on this chart represent every geotagged Tweet since 2009. The color represents number of tweets in the region, and the intensity shows where people move and tweet the most. (Note the maritime shipping lanes!) The chart was created using 20 lines of R code using the ggmap package.
Take a look at some other cities on Twitter's Flickr page, or read more about how this stunning map was created at the link below.