In descending order:
- Neft Dashlari: A Russian oil rig that got out of hand
- Manshiyat Naser: Cairo’s garbage town
- Miyake-jima: A Japanese volcano town that is frequently covered in deadly sulfurous gas
- Yellow Fleet: A small fleet of abandoned ships in the Suez Canal
- Dwarf City: A Chinese city full of little people
- Kowloon Walled City: An anarchic city of 33,000 in 0.01 square miles that apparently actually worked for thirty years, until the Chinese government tore it down.
If you’re looking for inspiration for a cyberpunk or distopian future setting, I’d start my research here. Wow.