Warning: This chart might break your brain.
Barcelona design concern Bestiario has compiled the population growth data for 590 cities and crammed it all into one intensely jazzy visualization. The timeline begins on the left side in 1950 and is projected forward until 2025, with each column representing a five-year period. (The data comes from mapmaker Nordpil.) You can highlight a city's growth by clicking on its color-coded line. They are stacked in order of population size, with Tokyo on top and... I don't know what's at the bottom, as my mouse can't click that precisely. Łódź, maybe?
If you're wondering what gives this chart its unique kick, it's probably the computer language, Impure, which Bestiario created specifically to spawn this kind of project. Here are a couple notes about the visualization from the Impure Blog:
"It’s crazy that if you take the 590 most populated cities you don’t reach the half of the urban population of the world.... That’s because the number of cities grows exponentially when the number of inhabitants decrease linearly....
"I found particularly insightful how Africa and Europe display mirrored shapes, they seem to be living different times in History. It’s quite evident the loss of population primacy of the big European cities since the end of the second war, when a lot of things happened (quick economic growth, european colonies independence, creation of the European Union, post-industrial social crisis)."