Just finished re-watching this short documentary from The Wall Street Journal on Kowloon Walled City. The documentary is directed by Diana Jou and is one of the best english-language video pieces on Kowloon Walled City that I've ever seen. They even interview the photographer behind City of Darkness (one of my all-time favorite books).
When the video was first published, it came along with an interactive WSJ minisite on the Kowloon Walled City.
But seriously, what a crazy place. If this were around today, I'd definitely venture in just to have a look. It's a rabbit hole of danger and surprise that is now replaced by a public park. If you want to know more, City Of Darkness is really your best resource for photos and stories from the people who lived there.