Megacities

Sixty years ago there were only two megacities - cities with over 10 million inhabitants - on the planet: New York and Tokyo. Now there are 23 and by 2025 the UN predicts there will be 37, all but eight in the developing world. The Guardian has a special interactive report investigating this trend - take a look at it here. Then have a look at the data.
The pictured city Shanghai is home to at least 20 million people, half of whom are immigrants from other parts of China.