I came across a video on Youtube discussing it (there are several), and Kowloon Walled City is just endlessly fascinating. A few notable videos I found on the subject were:
Kowloon Walled City: Hong Kong’s City of Darkness
Inside Hong Kong’s Kowloon Walled City
There is also a book on the city called City Of Darkness Life In Kowloon Walled City, which I found on archive.org in high resolution. It is full of photographs and detailed accounts of the comings and goings within the enclave.
It’s definitely my favourite of the 3.