This is 99% invisible.

I'm Roman Mars.

In 1898, China granted a 99-year lease to Great Britain for the areas across the harbor

from the British-controlled island of Hong Kong.

But smack in the middle of that territory known as Kalun 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 was the first photo that I saw of it.

Why don't you start describing it? I haven't, yeah, taken it in yet.

Okay.

The first analogy that that springs into my mind

is it looks a little bit like the

board cube from Star Trek. It's a city block and we're not looking at a neighborhood that's nestled in a city.

Like we're looking at a Borg cube that is in the middle of nowhere.

There's skyscrapers behind it, but the demarcation between this neighborhood and everything else is staggering.

That's my friend Nick Vanderculk from the program Love and Radio showing me photos. He was the first person who

told me about this place. It became known as Kalun Walled City. And even though the

walls eventually came down, its name was still appropriate.

There was no mistaking the boundaries between it and the rest of Hong Kong.

The edges became a wall of 13-story high-rises overlooking a comparatively sparse squatters village.

Buildings evolved organically, growing tendrils of bridges, pipes and wires that encroached on other

...