Before its demolition in 1993, Kowloon Walled City was the world’s most densely populated settlement. An ungoverned 6.5 acre tract on the edge of Hong Kong, it was home to 33,000 souls—which comes out to an eye-popping population density of 3,249,000/sq mi.
Kowloon Walled City’s “streets” were passageways only a meter or two wide, and one could follow a network of staircases and passageways from one end to the other without touching ground. It was, in short, one of the wonders of the modern world. Like those of the ancient, it’s lost and gone, but (unlike those) we have video:
Another document of the city’s life can be found in the remarkable images of Canadian photographer Greg Girard.