Inside Hong Kong's lawless 'walled city' - the most crowded place on Earth for 40 years

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.