Very interesting map created by the number of tweets, differentiated by "locals" (blue) and "tourists" (red). Especially looking at Japan, and specifically the Kanto and Kansai regions, you can see how the tweets outline the various railway lines quite clearly. You can even see a faint outline of Tokyo Station's platform 1&2 (Chuo Line). Even more pronounced are the terminal building outlines at Haneda and Narita Airports, in red.
http://www.citylab.com/commute/2015/02/where-do-locals-go-in-major-cities-check-out-this-interactive-world-map/385768/