The Kowloon Walled was a singular Hong Kong phenomenon: 40,000 people living in 350 high-rise buildings, built without the contribution of architects, engineers or government oversight, crammed into a single Hong Kong city block measuring 100x200 meters. Technically a part of China within the boundaries of British-controlled Hong Kong, it was, while it stood, the most densely populated place on earth. The Walled City was demolished in 1993.
The story of the the Kowloon Walled City is most thoroughly documented in City of Darkness Revisited. It updates Greg Girard and Ian Lambot’s influential original book, City of Darkness: Life in Kowloon Walled City, first published in 1993.