kowloon walled city
Chinas tiny enclave in british hong kong for decades was finally demolished in 1993.
Rising up abruply in the heart of urban hong kong 10,12 and sometimes 14 storyes high, there was
no mistaking it: an area 200 by 100 metres of solid building.
more info - http://en.wikipedia.org/wiki/Kowloon_Walled_City