Kowloon Walled City
You can get an idea of what it might have been like, although at a much more modern, safe, and smaller scale by exploring the Chungking Mansions in Kowloon: <a href="http://en.wikipedia.org/wiki/Chungking_Mansions" rel="nofollow">http://en.wikipedia.org/wiki/Chungking_Mansions</a>