99% Invisible: The most densely populated place on record

In 1898, China granted a 99-year lease to Great Britain for the areas across the harbor in the British controlled island of Hong Kong. But smack in the middle of that territory, known as Kowloon, was an enclave that wasn't included in the lease. A place that would, at least officially, still be controlled by the Chinese. It was a large fort, built decades earlier to put a check on British expansion. But it evolved into something very, very different. 

This story was produced by Roman Mars for his tiny radio show about design, 99% Invisible.