From the 1950s until 1994, over 33,000 people lived and worked in Kowloon Walled City, a massive complex of 300 interconnected buildings that took up a city block.
Caught between China and the British-run Hong Kong government, the city was essentially lawless, equally known for its opium dens and organized crime as its dentists' offices.
Photographer Greg Girard spent years investigating and documenting the strange place before it was demolished. Girard collaborated with Iam Lambot, another photographer, on a book about Kowloon, titled "City of Darkness Revisited," available here.
Girard has shared a number of photos from the project here, and you can check out the rest at the book's website.