♪♪ -An extraordinary hoard of lost treasure discovered in the Southeast Asian nation of Laos, 53 pounds of gold, silver, and precious stones, one of the most valuable finds in history.

-The number of objects, the size of the objects, the stage of preservation of these objects is amazing.

-But what does this exquisite treasure reveal about the society that made it?

Could it shed new light on the early years of the Khmer civilization that went on to build the great medieval city of Angkor, home of the spectacular temple of Angkor Wat?

Now, an international team of experts is using the latest technology to find out how these priceless objects were made... -How can I help to unravel this big mystery?

-...and to discover who might once have used them.

-Each process of metalworking leaves a mark on the object like a fingerprint.

-Using LIDAR to scan the landscape, the team finds new targets for archaeological investigation, where incredible discoveries are unearthed, including more gold and human remains.

-There are human bones.

Maybe it was a king?

-Their investigation into the treasure will take them through the jungle and on a grueling, once-in-a-lifetime expedition into the spiritual heartland of the mighty Khmer kings.

♪♪ ♪♪ In the city of Savannakhet in southern Laos, a priceless group of centuries-old artifacts is being moved to a secret location for scientific and historical analysis.

One of the most important archaeological discoveries ever made in Asia, the collection is undergoing an intense examination by an elite team of international experts.

Ten months ago, the team dated the treasure to around the 8th century.

Now, they're back again, with new experts joining the investigation.

Over the next two weeks, they'll analyze the treasure in meticulous detail, using state-of-the-art technology.

They want to find out how the items were made and what they were used for.

Anticipation mounts as the new team members wait to see the treasure for the first time.

♪♪ Finally, before them, priceless artifacts of gold and silver, more than 1,000 years old.

-The discovery of the treasure is major for the history of not only Laos, but Southeast Asia.

-Archaeologist and goldsmith Barbara Armbruster is seeing the treasure for the first time.

Barbara's an expert in the crafting of metals and alloys.

-Ah, ah, okay.

There's the base.

-Yeah, this is the base.

-Knowing what metals were used, along with the craftsman's tools and techniques, might give the team a clue to where the items were produced.

♪♪ At the start, there is intense focus on one of the stars of the collection: a kendi, or water jug.

-It's so delicate.

It's really the most beautiful object I've seen in this treasure.

-To reduce the handling of such a precious object, it's being preserved digitally.

[ Camera shutter clicks ] Pascal Mora is an expert in photogrammetry.

[ Camera shutter clicks ] -I use a turntable to be able to take picture on different angles.

-He takes hundreds of overlapping photographs, which computer software will stitch together.

-I have to take picture all around the object to be able to get all the detail.

-But before a 3-D model can be created, there's another step in the process.

Laser scanning will capture details that photographs can't, like surface texture.

-So, combining the two techniques, we are able to produce the best possible 3-D model with good geometry and good color.

-The kendi is now digitally preserved for the future.

The team will use the digital models in their quest to learn the origins of the treasure.

♪♪ ♪♪ The Khmer temple site at Vat Phou lies in southern Laos, five hours south of the treasure vault.

The team believes that this area could have been the original home of these exquisite artifacts.

-Vat Phou has always been in the Khmer inscriptions, in the Khmer history, the most venerated place.

It's a very sacred place.

-The Vat Phou temple sits at the foot of Mt.

Phu Kao, three and a half miles from the Mekong River.

In the 8th century, the royal Khmer city of Kurukshetra was located here on the riverbank, within walking distance from the temple.

♪♪ Today, a small fishing village occupies the site of Kurukshetra.

For the treasure team, this city from the past is now of significant interest.

Learning more about life here may shed new light on the priceless artifacts.

-One here, one here.

[ Speaking foreign language ] -The team led by Christine is beginning a major new excavation on the edge of Kurukshetra.

Inscriptions on a stone stele indicate that this city and the temple at Vat Phou may have been very prosperous.

-Yes, you can put here.

-The team wants to know more about how early Khmer society was structured.

And LIDAR technology, which can reveal evidence of buildings long gone, is opening a window into the past.

This is the first LIDAR map of Kurukshetra.

From the largest features, like the huge boundary canals, down to the mounds where individual structures once stood, this new survey allows the team to target their excavation with pinpoint accuracy.

And one site, on the outskirts of the city, stands out.

At ground level, there is little to see with the naked eye.

But the LIDAR data shows the team where they should begin their investigation.

-16... -The length, width, and depth of the area to be excavated can be carefully plotted.

-So, this is four meter by four meter.

It is the grid of our excavation.

-The site's layout is a familiar one, piquing the team's interest.

-On the middle, a working area, maybe for the servants.

On the south, a sacred area.

So, it's compatible with the palace we know in Angkor.

-The realization that the footprint of the dig site resembles that of much later palace sites in Angkor is evidence there might be strong connections between this early city and the great capital that the Khmer people constructed in the centuries that followed.

The excavation of this site might shed new light on the pre-Angkorian society that crafted the treasure.

Back at the treasure lab, attention has returned to another one of the most significant pieces in the collection: the golden box.

Barbara is searching for clues to how it was made and what it might have been used for.

-We are going step by step, very close to the object.

Each process of metalworking leaves a print, a mark on the object like a fingerprint.

And if you see that, you can deduce how the thing was made.

-It is clear the box was made by a master craftsman.

-The goldsmith uses a gold sheet, which is hammered by striking with a hammer and on an anvil.

And starting from that, he is creating a three-dimensional shape.

-But the longer Barbara works with the box, the more she questions what it's actually made of.

-At the first sight, to me, to be got in gold, but having a closer look, I don't know.

-Perhaps the golden box is not 100% pure gold after all.

♪♪ At the Kurukshetra site, the team is digging through the Earth's layers of history, moving back to the early days of Khmer power in Southeast Asia.

-Each time we change level, usually it's 10 by 10 centimeter, we take another level.

-Any artifacts within the layers could be minute.

-They know perfectly what to do, and they know perfectly what to look, what to take out, what is good and what is wrong, what is not necessary to keep, because they are working with me since 2009.

Mon -- She work with me since 30 years.

She's able to find one millimeter by one millimeter gold leaf.

[ Chuckles ] Incredible.

I don't know how she do.

[ Laughs ] She's very good.

-Several layers have now been removed, exposing the earth to light and air for the first time in hundreds of years.

But have they dug deep enough to find anything from the pre-Angkorian period?

It's up to Christine's experienced eye.

Spraying the exposed dry, dusty surface with water will reveal any color variations.

These variations allow the archaeologists to identify sections in the wall that are called cultural layers.

-Here is different than here.

-And they have found evidence of human habitation.

The discovery of the cultural layer associated with human occupation of the site is a milestone for the team.

The search for any historical artifacts left behind now intensifies.

♪♪ After painstakingly combing through layer after layer of earth at the dig site, finally, a breakthrough.

The top of a pot is revealed.

Excavating with such care is a time-consuming process, but the team is making real progress.

And Christine is called to inspect another discovery.

On the floor of the trench, part of another pot.

-There is a lot of small fragments.

-Yeah, and you -- you see when we remove the... -Yeah, you take out the... -Yeah, take out one part of the pot.

-Yeah.

-Finding the pots is an encouraging sign that they're digging at the right level.

-And you see the charcoal.

They have the charcoal everywhere.

-There is a lot of charcoal, so it means that people lived on this level.

There is a lot of things now.

Before they found nothing, nothing, nothing, and now we have the level where people live.

With all the charcoal, it means that maybe it's a cooking area.

♪♪ -As the team digs down further... -Oh, I see something here.

-...they make a startling discovery, revealing the wealth of this ancient site.

-Here it's yellow, yellow.

-Unearthing the two pots now pales in importance.

-It's quite the middle of the hiding place.

-The team's incredible find is unlike anything ever seen before in the history of archaeology in Southeast Asia.

Nine exquisitely crafted gold lotus flowers lie beneath the bricks they've unearthed.

-It is unique because it is the most earlier pre-Angkorian period we have.

On all the area of Vat Phou, it's the first time that we found some kind of thing like this.

It's very, very fragile because it's very thin.

Gold leaves is very thin, you see?

Less than one millimeter.

We have to keep it very carefully.

-Is it a lotus?

-I think it's a lotus flower, yeah.

-In Buddhist symbolism, the lotus represents purity of the mind, body, and speech.

But lotus petals made of gold aren't the only man-made objects here.

-Also, we found, close to the flower, a belly button.

-These terra-cotta belly button ornaments were an important symbol for Buddhists and represented the main energy center of the body.

-It means the middle, most important part.

-Yeah, yeah, the most -- the most important part.

-It was like this.

-Yeah.

-And the flower was quite close to this, and the other flower everywhere like this.

-The discovery of Buddhist artifacts here provides a snapshot of Khmer life in Kurukshetra in the centuries before the great Hindu city of Angkor was founded.

-So, in that time it seems that Buddhism and Hinduism can be close to each other without fighting and without nothing problematic between the two religions.

-The suggestion that Buddhists and Hindus lived together harmoniously can also be seen on the golden box, which features iconography from both religions.

The golden lotus flowers, the oldest ever found, are further evidence that this region is where the treasure could have originated.

But there's still more to uncover because the team quickly realizes the lotus flowers are merely a decorative covering for what lies beneath: cremated human remains.

-I am sure that it is cremated bones because bones un-cremated and bones cremated are totally different.

It's the first time for us to find bones and gold deposit in the middle of this kind of place.

-Given the volume of bone fragments, it would seem that only half of a cremated body was interred here.

-If you burn a body, there is more bones than this, so maybe it's only one part.

And maybe the other part of the bones in the Mekong River because the Mekong River is also a sacred river.

-The practice of cremation and the impact of the region's hot, humid climate and its acidic soil mean that few ancient human remains have ever been found in the area.

According to Christine, these are the oldest bones ever discovered from the Khmer era.

And the golden petals placed on top suggest who this person might have been.

-They want to give more importance to these bones.

Otherwise they will not put gold on those bones.

So, this is very interesting.

Maybe it was a king?

-The team's growing understanding of the site's layout supports their theory that the remains could be royal.

-If what I think is correct, that the big building was a palace, you have a funerary area, and it could be the place where they put the king after dying.

And that's why they put also gold leaves on the bones, to never forget that it was a very important person.

-It's an incredible thought.

The remains discovered here could be an early Khmer king.

Christine believes the find could date from as early as 450 A.D., 200 to 300 years before the treasure was likely made and about 700 years before the Khmer empire reached its peak in Angkor.

The discovery of gold and the possible remains of royalty provides further evidence this was once a place of significant wealth and power.

Could this be the kind of place where the treasure might once have belonged?

There were few places in the Khmer empire with the resources to craft the type of elaborate objects found in the treasure.

Determining the exact composition of the metals used to make these items might help to reveal exactly where the raw materials came from, a critical clue in piecing together the origins of the treasure.

-Here comes the masterpiece.

-David Bourgarit is an archaeometallurgist, an expert in ancient metal-making techniques.

He will examine the box in hopes of determining what it's made of.

-So, you see a very high relief, which is nearly three-dimensional here.

This is really something special.

And we find it also on the kendi.

-And Barbara has a new theory to share.

The archaeologist originally assumed the box was made of solid gold.

But now, she isn't so sure.

-In the first look, I thought this must be plain gold.

But now I'm wondering if it's made of gilded silver.

And so, it would be very good if you could show us that this also is gilded or the contrary.

-Gilding is a technique by which a thin layer of gold is coated onto another surface, usually another metal.

David has special tools that will offer preliminary insight into the composition of the box.

-So, I have the light here and I have also a camera, which enables me to focus on the place I want to be.

-The X-ray fluorescence scanner analyzes the makeup of an object, creating an elemental fingerprint.

And the results suggest that the box's appearance is misleading.

-So yes, there's a lot of silver, which shows that this cannot be gold.

So, we have one answer.

-But David's X-ray scanner has limitations.

-The apparatus we have is not able to distinguish between a mass of gold, solid gold, and gilded silver, a layer of gold on silver.

-For clarity, the team now turns to 3-D scanning.

By precisely measuring the dimensions of the box, they can calculate its volume.

Knowing the volume allows them to estimate what its weight should be if it's solid gold, one of the heaviest precious metals.

It quickly becomes clear that it's not heavy enough.

It seems that Barbara's hunch is correct.

The box is not pure gold.

-Because of the volume and the weight, it can only be made of silver, silver with a gilded layer.

But the gold layer is so thin that it does not impact the total weight.

So yes, that's where we arrived to.

-So, your hypothesis was good, so it is -- so it looks like gilded silver.

-Well, it's what we expected.

But as the cover is so well gilded, at the first look it seemed to be gold, yeah.

-The next step is to find out where the metals were mined.

Silver is abundant in Asia, making it hard to pinpoint where it was extracted.

But gold is rare and can have distinguishing characteristics.

Could the precious metal have come from the Vat Phou area, where the team thinks the treasure might have been made?

♪♪ Gold comes in many shades of yellow.

To an experienced eye, those shades are clues to where the gold was mined.

Pasitsay Syphakdy is a local goldsmith.

After studying the box, he gives the team his opinion.

-[ Speaking foreign language ] -According to his experience, this gold may belong to Attapeu, one province in the south of Laos.

-Attapeu Province is located in southern Laos, about 25 miles from Vat Phou.

People still pan for gold there today.

The use of Attapeu gold on the box is the strongest suggestion so far that major artifacts in the treasure might have come from the area around the important temple site of Vat Phou.

Could the same source of gold have been used for both the box and the kendi?

[ Conversing in foreign language ] -So, he says that the color, the composition of this kendi, it's exactly the same as the box.

-So, this is the type of gold from Attapeu region?

-Yes, according to his expertise.

♪♪ -Knowing the gold came from near Vat Phou supports the team's theory that items in the treasure collection were made to be used at the temple.

♪♪ And other items in the collection appear as though they might also have been used in religious ceremonies.

The ornate candlesticks are a case in point.

♪♪ -The candlesticks, there are two major parts that we know.

By the rivet holes on the upper part, there must have been something still fixed on it, which we didn't find in the treasure.

So I think there must've been some shallow bowl on it, fixed, and most probably for burning incense.

-And what is interesting is that it is lotus petal.

-Mm-hmm.

-And usually, lotus petal is used for religious purpose.

-It's for offering or...?

-Yeah, you can find this kind of design on the temples.

-The team is confident that objects like these would not have been out of place somewhere like the temple of Vat Phou.

But why did the Khmer build a temple there?

Inscriptions on a stone stele reveal that this temple remained important to the Khmer kings long after the decline of nearby Kurukshetra and the establishment of a new capital in Angkor to the south.

Why was this temple site at the foot of Mt.

Phu Kao so important to the Angkor kings?

Christophe and David Bazin are heading into the countryside to search for evidence of a lost highway that stretched between Angkor and Vat Phou, mentioned in ancient inscriptions.

Understanding the connections between these great sites could explain why Khmer leaders valued this area so highly and may shed new light on the links between these kings and the treasure itself.

-So, here we go on the left.

-The archaeologists use satellite signals to align their current location with data from the LIDAR map.

-I switch from satellite to LIDAR.

We have 300, 400 meters to go.

We are more or less on it.

-Leaving the car behind, they take to footpaths across the fields.

At ground level, there's nothing to suggest this place might once have been a significant location.

But laying the LIDAR data over the modern landscape... ...provides an astonishingly different view.

Christophe and David's footpath is no ordinary footpath.

From Vat Phou, it stretches away to the southwest and continues on for 180 miles.

A vast highway, leading all the way to Angkor, just as the inscriptions described.

-It is strange how this road looks amazing on the LIDAR itself.

But on the ground, there looks like nothing.

-Inscriptions describe how this ancient highway was once a major trade route with raw gold from Attapeu being transported from Vat Phou to Angkor.

-The road was linking settlements, was linking cities, and also other types of shrines, settlements, probably hamlets, built along the road.

-The original road surface is long gone, but evidence of this vibrant lost world can sometimes be found in what is now farmland.

-Oui, une ceramics.

-Yeah, so it's a ring.

-So, I will mark GPS point, 1637.

-Yay, it may be a roof tile.

Oh, yeah, that's great, the top part of a bottle.

-This is very nice.

-Uh, can't you find a bigger one?

[ Laughs ] Wow, that's a nice one, this beautiful design that's on the neck of a round bottle like this.

With nice decorative motifs here, with vertical lines.

It's very diverse, huh?

Good, good, good.

Ey, regarde!

That's the antefix on the edge of the roof, with lotus petal, with different flames around.

So, that's what's making the rim of the roof quite beautiful.

-The lotus leaf design on the tile suggests it could date from the time when Angkor was flourishing.

But this was much more than just a bustling trade route.

The LIDAR scans show that the highway was 30 feet wide, far bigger than needed for simply moving goods.

Inscriptions record that this was a royal highway, made for kings.

-Why do kings travel through their kingdom?

Just to show that they are the kings.

It is important to go through their own kingdom to venerate the people, to show also their power.

-But flaunting their power wasn't the only reason for the kings to go to the great temple site of Vat Phou.

Looking toward Vat Phou, and once again using the LIDAR map to position themselves, Christophe and David can see why the kings traveled this carefully planned road.

-If we just take some steps aside, we can really see the -- this alignment.

-There ahead, greeting any traveler from the southwest on this last section of the highway and towering over Vat Phou is the sacred mountain of Phu Kao.

Inscriptions state how gold was moved from Vat Phou to Angkor.

But heading the other way on this grand highway were Angkor's great Hindu kings.

And this mountain was the reason they came.

It is no accident that the Hindu temple site of Vat Phou, constructed over many centuries, is located at the foot of Mt.

Phu Kao.

Hinduism and Buddhism had long coexisted throughout the region.

But Hinduism was the predominant religion, with the god Shiva considered the supreme being, as seen on the temple's walls.

Devotees worshipped phallic-shaped objects called lingas, earthly representations of Shiva himself.

The most sacred lingas weren't man-made.

They occurred naturally, in the landscape.

And Mt.

Phu Kao, topped with a natural 60-foot sandstone pinnacle, was the most sacred linga of all.

Hindus believed it was the home of Shiva.

The temple of Vat Phou and the neighboring city of Kurukshetra were built in its sacred shadow, hundreds of years before the treasure was made.

♪♪ From the 9th century on, the Khmer empire expanded, with the great temple of Angkor Wat constructed in the city of Angkor in the 12th century.

Inscriptions reveal that the kings of distant Angkor would continue to travel the highway to the Vat Phou temple, despite the neighboring city of Kurukshetra's decline.

A royal procession of this size must have been a stunning sight.

-Depicted on one beautiful bas relief in Angkor Wat, we see, actually, cavalries, we see generals, the troops, the priests, musicians, the king, his guards, his courtesans, and the princess and all the rest.

And so it's a very long procession.

It would've been quite spectacular.

-A huge investment of resources would have been required to make a royal pilgrimage of this size happen.

♪♪ Evidence of the Khmer kings' devotion to Vat Phou.

And there are similarities between the buildings in Angkor and those at Vat Phou.

♪♪ Some of the most impressive ones still standing here at Vat Phou were commissioned by the same king responsible for Angkor Wat in the 12th century.

And earlier Khmer kings also made significant offerings.

Structures that predate the rise of Angkor can be found across the site, including ones built at the same time the treasure is believed to have been made.

And the team's analysis of the treasure itself reveals how lavish and varied royal gifts to a temple could be.

-So, Dominique, I will show you something very interesting for you, and beautiful and one of the major pieces of the treasure.

Look.

As you can see, it is the shape of a boat, and you see there is a beautiful inscription.

-Dominique Soutif is an expert in ancient inscriptions.

To decipher the words on the fragile bowl, he makes a mold of the inscription by easing damp rice paper into the delicate relief of the text.

-Actually, it's a bit like when you're a kid and you put some pencil on a coin.

-Adding ink onto the damp paper creates a highly accurate copy of the inscription.

-You want another piece?

-Let's see if it works or not.

-It's a long and delicate process.

But finally, the meaning of the inscription is revealed.

-The silver vessel mentions a large donation of vases, lands, and everything you need for the temple.

-The detail of the list is astounding.

Gardens, male and female slaves, fields and shapely lambs, and dishes for the daily worship of Shiva.

-It's a list of objects which were given to this god.

It's a big royal donation made by a king.

This donation was incredibly generous.

-The discovery that the silver bowl lists royal offerings to a temple is of enormous significance.

The team now believes that other objects may once have served a religious purpose as well.

-Because the inscription proves that they are directly dedicated to gods, we can be sure that all the objects of the treasure were coming from sacred temples.

-But if the treasure collection itself was a royal gift to a temple, was it used in religious ceremonies?

Dominique explains the rituals performed in Khmer temples.

-This daily ritual for a god is comparable to the service of a king.

You are offering to the god exactly what you would do for -- to the king in his palace.

And you have to wake him up, to bathe him, to offer him food, incense, and to sing for him, to dance for him, and so on.

-The god, represented by a linga housed in the central sanctuary of the temple, would have been tended to by high priests.

The treasure could have played a key role in these sacred rituals.

-With the treasure that has been discovered, there are at least four objects which were offered to gods.

The boxes were probably used to store incense.

The plates were dedicated to serve food.

The kendi, probably for the bath.

-Bathing the god in the central sanctuary would have been one of the most significant parts of the ritual, one which required the most exquisite objects.

-The kendi is a very rare discovery in gold.

I think the only one which has ever been discovered for the pre-Angkorian period.

This is quite exceptional, actually.

It was probably used to pour water, especially if it's for the bath of the god.

-In Khmer mythology, water was sacred, and rainwater falling on the natural linga at Mt.

Phu Kao was considered the most sacred of all.

It flowed down the mountainside to a holy spring, where the Vat Phou temple complex was constructed.

Christine is exploring the site to see how these sacred waters were channeled right through the temple.

Archaeology has shown that the Khmer people were masters of hydraulic engineering.

An elaborate network of pipes once existed here, channeling water down the mountainside and into the temple itself.

-They take the water... -Uh-huh.

-...and from here to this entrance... -Through the...?

-...through the hole... -Uh-huh.

-The channel on some column was going down, to go inside the temple, the brick temple, and bathe the linga of Shiva.

-Uh-huh.

-Permanently.

And this spring is very holy because it's coming from the top of the mountain, where Shiva is sitting and meditating.

♪♪ Come, Souliya.

I would like to show you the main place of the sanctuary.

It was on this brick area that the main linga of the Shiva was.

From the sacred spring coming from the top of the mountain... -Yeah, yeah.

-...the water was coming by some channel in sandstone, from the spring until here and going... -Through this?

-...through the wall on this way to bathe Shiva permanently by the holy water of the spring.

-The exquisite golden kendi could have been used in these sacred ceremonies, possibly in the presence of the king himself.

-Arriving on the main access to the Vat Phou temple, we can imagine that the king or high dignitaries were visiting the main temple and honoring the god inside the temple.

-But having arrived at the temple, would their journey have ended here or could the kings have ascended the sacred mountain to worship the holiest linga of all?

Ancient writings suggest the kings of Kurukshetra might have done this, long before Angkor was founded.

A Chinese text from around the 6th century describes a temple to Shiva guarded by 1,000 soldiers at the summit of a mountain.

Is the text about Vat Phou?

♪♪ [ Metal ringing ] Would climbing to the top of Mt.

Phu Kao have been the most important journey a Khmer king could make?

Devotion to Shiva was how kings justified their authority.

-There is no doubt that people went there for worshiping in ancient times.

-To find out more, the team is preparing an ascent of their own.

On their journey to the top, they will be searching for evidence of religious ceremonies from the pre-Angkorian era.

The climb will take two days.

Even today, the mountain is considered sacred.

Access is restricted, with strict rules in place.

Bad thoughts are not to be taken on the ascent.

♪♪ To assist their search, the archaeologists have LIDAR-scanned the entire mountain for the very first time.

But conquering the mountain will be no easy task.

Mt.

Phu Kao rises over 4,500 feet above sea level.

Any unusual features appearing on the LIDAR scans will be explored by the team as they ascend.

♪♪ Over time, landslides and erosion have buried sections of the mountain path.

But this climb would never have been easy.

♪♪ Inscriptions from the time decree that no one could be carried up the mountain.

-That means everybody had to walk the same way we did.

Kings, commoners -- Whoever actually had to come and worship the god on top of the mountain had to go that way.

So, it's good to share that feeling in a way.

-The meditative nature of climbing through this sacred landscape would have been part of the religious experience.

-When you enter a sacred space, it's very important to have, like, good thoughts, being very focused on why you are doing this walk and where you want to go.

-There are various inscriptions since the beginning of the Angkor and pre-Angkor period referring to the mountain as the presence of Shiva.

But beyond, it's the whole mountain, which somehow is the god himself, and as such is a kind of a sanctuary.

It's totally sacred, and the inscription refers to that area as protected, like a kind of heaven where you can't hurt human beings or animals, where everybody should be somehow protected, but where also you have to enter with a positive mind.

♪♪ -We cannot access to the top in one day.

It's too difficult and we will use too much time because the final ascension, the final climbing, it's very difficult.

So, we have a base camp at maybe two hours from the top.

-Happy to stop walking for the day.

-It was exhausting.

[ Laughs ] It was really hot.

-After a whole day of climbing through the jungle in extreme heat, the team has covered less than five miles.

But they are just over 600 feet below the summit, within striking distance of the holiest site in the Khmer world of the past.

-Maybe we will understand more tomorrow about why the king needed to come here.

♪♪ ♪♪ -At first light, the team leaves camp.

The sacred summit looms high above.

-It's really beautiful, but it's going to be really steep at the end.

-The jungle is now so dense, the LIDAR map is needed to safely plot the rest of the route.

-We are just on the ridge here.

We are going this way, and depending where the track will go, it may be interesting just to divert rapidly to see that stuff.

-A shape on the screen has caught Christophe's eye.

-Wow!

-There is a depression here?

-This is... -Yes, and where you want to see?

-The structure looks man-made.

-Yeah, it doesn't look like any natural thing we have seen before.

-But the foliage is too dense to find anything at ground level.

-Yeah, sure, it's very difficult sometimes under such vegetation to make sense of these kind of features.

-A detailed archaeological investigation is needed to find out more.

But the suggestion of human activity here means the team is on the right track.

♪♪ A final scramble takes them to the foot of the huge natural linga crowning the mountain.

♪♪ Finally, evidence of those who went before them.

-The style of that linga suggests it's a pre-Angkorian one.

Clearly people have been worshipping here -- priests, pilgrims -- and so why not the kings even -- even made the climb too?

Why not?

-Being in that sacred forest, that sacred mountain, it's something very touching.

-On the sandstone wall of the linga itself, the team spots something that also appears on some objects in the treasure...

Evidence of Buddhism.

-You see the wheel here.

It's a very common Buddhist symbol, which have been long found for thousands of years in Buddhist shrines.

But what is really interesting is to see how this place remains sacred through different religions, by different pilgrims, worshipping different gods.

-The archaeologists have now seen multiple examples of Buddhist and Hindu symbolism together.

Perhaps sacred artifacts from the treasure were used in ceremonies here at the foot of the linga.

But did any of the treasure make it to the very top?

Only 60 feet remain.

But they are the hardest.

-No, you've got to take all that slack through.

No, just stop climbing.

That's it, get your knee up on up there, you're doing great.

♪♪ -Oh, wow!

Can we see Vat Phou?

Right there?

That's amazing.

-I can clearly understand the feeling of the people.

To be on the top of the top, to make a link with the god, I can feel this.

-Any king that made it up here would have looked out across the vast expanse of his domain.

-The ancient road is quite visible from the city here, going down and lost in the haze for over 200 kilometers, going to Angkor.

-But there's far more here than just the epic view.

-I'm surprised actually.

There was a kind of pedestal of some sort, probably another very small linga.

But only these small fragments are the witnesses of all the ceremonies which would have taken place here.

-Christophe had no idea that these relics were here.

From their shape, he thinks they predate Angkor.

-Who would have come here?

Kings, priests, commoners.

We don't really know, but clearly people who may have come here full of devotion.

-Whether objects from the treasure made it up here will never be known.

But given what the team has learned about these stunning artifacts, they believe it's possible.

-Performing a ritual here, you will need various objects, candles or incense sticks.

The golden kendi is a perfect example of the kind of object which could have been brought in to be used for the rituals to worship.

You are really on the top, the closest to the god, where your prayers and the rituals you will perform will be the strongest.

-This is where the sacred water flowing into the Vat Phou temple begins its journey down the mountain.

-If it's raining and the rain is like going on top of the linga and going down to the rivers and going to the city, so it becomes like holy by the fact that it's... -Completely.

Exactly, yeah, yeah.

This water, which is actually the source of life, would have come first on the head of Shiva, going, pouring through the mountain, through the rivers.

And it will actually sanctify the whole territory, which is the best guarantee of power, to have this sanctified water not only in the rice fields around, in the ponds and so on, but also in the sanctuary of Vat Phou.

-This mountain and the sacred landscape around Vat Phou could well be the place where the treasure truly belonged... ...where some of the first Khmer kings constructed their earliest temples.

And over successive generations, even after the capital city moved to Angkor, Khmer kings returned here on their great highway to the cradle of their civilization so they could venerate the god who gave them the power to rule.

♪♪ By opening a new window into the rise of this great civilization, the investigation into the treasure highlights how the epic story of the mighty Khmer empire didn't begin in Angkor.

When the treasure was made, Khmer society was flourishing here, around this sacred mountain, long before the rise of Angkor.

♪♪