[dramatic music playing]
MALE SPEAKER: This is it, Albert.
Welcome to the jungle.
We are on sacred grounds right now.
You're just beginning to see part of the structures.
ALBERT LIN: I've never seen anything like this.
MALE SPEAKER: Welcome to Nan Madol.
ALBERT LIN: (VOICEOVER) Only a tiny fragment
of the legendary Soudelor city can still be seen.
Mangroves choke whatever else remains.
Now, new technology can help unlock
the secrets of this place.
How and why it was built, and just how big it really is.
What is that?
It's incredible, isn't it?
I was born here.
But every time I come up here, I'm always amazed.
Always.
This is the main ceremonial center of Nan Madol.
[majestic music playing]
ALBERT LIN: (VOICEOVER) It's a temple
to the island's ancient rulers, constructed
from pillars of basalt rock.
800 years ago, this place would have been bustling
with hundreds of priests, attendants,
and the feared Soudelor kings.
Must have been some super-powered humans
to build this, huh?
Well, this area was meant only for the elite.
It was the only time in our history
that we were ruled by one person, almost like a dictator.
So he was able to command all the people
on the island to come and assist in the building of Nan Modal.
Look, is that more rocks over there?
Is that even more of them?
That's an outer wall, built all the way
to the edge of the reef.
Yeah, you can see the reef breaking, right there.
Exactly.
It's massive.
ALBERT LIN: (VOICEOVER) To get to grips
with this "city in the sea," we need to work
out the full extent of it.
And that can only be done from above.
I think we have to scan this with the drone.
And maybe we can start to really map out
all these different features.
OK, so this is where we're at right now.
There are 90-plus structures, all man-made.
From here, all the way down south.
You had your exit-- - All the way to there?
Yes.
Such a huge area.
It is huge.
Can't see anything.
It's all mangrove.
Were the mangroves here 800 years ago?
No, I doubt it.
It's been abandoned for a long time, so mangroves just grew.
It would have been easier to map it then than it is now.
Well, that's why we have LIDAR, right?
We're gonna delete the mangroves.
Taking off.
[drone whirring]
ALBERT LIN: (VOICEOVER) My drone team begin the first of more
than 40 planned flights.
We're scanning this whole area, almost half a square mile--
twice the size of the Vatican City.
We want to strip back the jungle canopy
and reveal the rest of the city.
[dramatic music playing]
I'm going back to explore the gigantic building that Gus
showed me to find out more about the people who
built this place.
Why is there so little known about the people that
built this incredible monument?
The reason there is so little known
is because there's not a written system to express ideas.
It's through oral tradition, which are--
Stories.
Exactly.
Those are stories handed down, generation to generation.
And no person can tell the entire story because there's
the belief that, if they tell the whole story,
that they will die.
They're no longer useful.
ALBERT LIN: How was this place built?
I can't imagine how human effort could actually
carry these stones all the way up to the top of this building.
It's really not clear to us how it was done--
the physics part of it.
One legend talks about magic being used to lift the rocks
and bring them over here.
So they would fly.
Magic flew these rocks here.
That's right.
ALBERT LIN: (VOICEOVER) This whole expedition
is something else.
I'm a scientist, a technologist.
I deal in facts.
Finding out how they actually built this?
It's going to be a challenge.