More than 7 million inhabitants, 6500 per square kilometer, 17,000 per square mile, Hong Kong is one of the cities with the highest density in the world. There are housing complexes, where, if you live on the ground floor, you never see the sunlight and you have to have lunch with the lights on. This Quarry Bay building, in the Hong Kong island, it is a good example. When the need reaches the insanity.