Started playing with geonames.org's datasets. The image above displays cities with population above 1000. The higher the line for a city the more people live in it. The labeled cities have more than 5 million people. In total the location and population of more than 80000 cities was analysed for this image.
Done with www.processing.org.
Be sure to see it in higher resolution.
If you like it, digg it.