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Nova - Season 53 Episode 2 - Angkor: Hidden Jungle Empire
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00:13An iconic temple.
00:15The largest religious monument in the world.
00:18Angkor Wat is an enduring enigma.
00:21The engineering feat of Angkor Wat is unbelievable.
00:25In the heart of one of the greatest ancient cities ever built, Angkor.
00:29One of the largest, if not the largest, city in the world at the time.
00:33Home to over 1,000 temples.
00:36Each new king would try to outbuild the reign before
00:39and build a bigger and more impressive temple.
00:42But then the temples and the city were engulfed by the jungle.
00:46It mysteriously was abandoned.
00:49Or so the story goes.
00:53There are few clues.
00:55Almost every wooden remain and the vast majority of structures at Angkor were built in wood
01:01deteriorate very, very quickly.
01:04And many mysteries.
01:06The lack of bodies.
01:08One million people, not a bone, not a cremated remain.
01:13It's fascinating and frustrating.
01:16There's another story there sitting underneath.
01:18Now, archaeologists are using the latest technologies to reveal Angkor's hidden secrets.
01:24Sarah took the LiDAR data.
01:26She used some machine learning algorithms.
01:28To see through the jungle.
01:29The LiDAR data is absolutely mind-blowing.
01:32It was all an infinite landscape.
01:34And look into the past.
01:36I really like the pages of a history book.
01:38To find new evidence of a great civilization.
01:41They didn't just build Angkor Wat, which is a spectacular temple, right?
01:44Like, they were transforming the entire landscape.
01:47Angkor.
01:48Hidden Jungle Empire.
01:50Right now on Nova.
02:11In the jungles of Cambodia, a spectacular ruin rises from the trees.
02:17This is Angkor Wat.
02:21A 900-year-old temple filled with intricate carvings and mysterious figures.
02:28It is the largest religious monument in the world.
02:32And a masterpiece of ancient engineering.
02:36The engineering feat of Angkor Wat is unbelievable.
02:40It's amazing.
02:41Angkor Wat is the centerpiece of the ancient city of Angkor.
02:47A marvel of vast infrastructure.
02:51Built with a network of human-made canals.
02:54And enormous reservoirs.
02:56Angkor was the heart of a wealthy and dynamic empire that thrived for 600 years.
03:03Then, around 1300, suddenly the buildings stopped.
03:07This vast, ornate city was largely abandoned.
03:12Why?
03:13Archaeologists like Pip-Al-Hang are trying to answer that question.
03:17And to understand the people of Angkor.
03:20Monumental architecture like Angkor Wat has been its signature.
03:24When you talk about Angkor, it's monuments.
03:27Part of my archaeological endeavor is to understand Angkorians people's life.
03:33What did they do?
03:35What was the relationship between the people and the city?
03:38The relationship between the people and the temple?
03:41And how did that change through time?
03:52The ancient city of Angkor was one of the biggest pre-industrial cities in the world.
03:58Located in Cambodia in Southeast Asia, its legendary temple, Angkor Wat, is its most iconic structure.
04:06But Angkor Wat is the largest of more than a thousand temples, spread across more than 150 square miles.
04:18A lot of these temples have really been left to the jungle.
04:21So trees are overgrowing them, the vegetation is everywhere.
04:24And when you walk into them, you sometimes feel like you're the first person that stepped foot in them for over a thousand years.
04:31The temples themselves have a sense of mystery to them.
04:35You don't know exactly what happened here or why they were abandoned.
04:38This land has been home to the Khmer people for thousands of years,
04:43living in small kingdoms often in conflict with each other.
04:47Until the year 802, when Jayavarman II defeated his rivals
04:53and declared himself a god-king in the Hindu tradition and founded the Khmer Empire.
05:03Nearly 100 years later, the capital of the empire was moved to a new site on a fertile plain, the city of Angkor.
05:14Over the next 500 years, the empire became the dominant power in Southeast Asia, ruling over all of what is now Cambodia and much of Vietnam, Thailand and Laos.
05:27The kings, who were considered holy, ruled both political and spiritual life.
05:32Each successive ruler strove to demonstrate his greatness through major construction projects.
05:38Each new king and each new reign would try to out-build the reign before and build a bigger and more impressive temple.
05:45As Angkor grew, so did the temples, in number and size.
05:51Until the 1300s, when temple construction abruptly stopped.
05:57Evidence suggests that by the mid 1400s, Angkor stood empty.
06:08It mysteriously was abandoned.
06:14Or so the story goes.
06:16And so this place has attracted the fascination of people from around the world for many, many hundreds of years.
06:24Partly because the city itself is so prodigiously massive.
06:28And partly because all of this was apparently left to the jungle by the Khmer.
06:34The abandonment of Angkor is an enduring mystery.
06:38Who were the people who lived here?
06:41And why did they leave?
06:43The answers are important.
06:45Not just for the archaeologists who are excavating here.
06:49Many Cambodians identify as Khmer and are deeply invested in this ancient place.
06:57Angkor is central to their heritage, connecting them to their ancestors.
07:03Angkor holds a profound place in Khmer life.
07:08The very word Angkor is deeply rooted in our national identity.
07:14Angkor, we can say for the Khmer people, it's our soul.
07:19Every one of the Khmer people say that we want to see Angkor before we die.
07:23But the full truth about Angkor and its people has been elusive.
07:28Because so much of the city has long lain hidden beneath the jungle canopy.
07:33We only know of Angkor what this one square kilometer temple as being a religious temple.
07:42A sacred space.
07:43But were there any people living inside Angkor?
07:46We did not know yet.
07:48We also tried to map the area and the vegetation was too thick.
07:52It was overgrown.
07:54It's incredibly difficult for archaeologists to map the center of Angkor
07:58where all the large temples are because of all the dense vegetation.
08:01But now, with the help of new technology, archaeologists are trying to see what has been invisible for centuries.
08:09And that's where the LiDAR data comes in.
08:12LiDAR is a powerful laser technology that has recently become a game changer for archaeologists.
08:18LiDAR has been absolutely revolutionary for our field of archaeology
08:22because it allows us to see the ground floor underneath dense vegetation.
08:27We acquire LiDAR data by putting a drone or a helicopter or a plane in the air with the LiDAR device on it.
08:33These devices send out millions of pulses of light.
08:36Most of those pulses bounce off things that we're not interested in, like buildings or trees.
08:41But some of them critically reach the ground surface.
08:44What we do is we measure the time that it takes for those ground returns to return to the LiDAR device.
08:50And using those measurements, calculate distance.
08:54With that information, we can then strip away all the vegetation so we can clearly see these archaeological features.
09:01The LiDAR scans revealed the breathtaking size of the city.
09:07The data was spectacular.
09:09All of a sudden, we could see these elements of the urban space that were completely invisible before.
09:15The LiDAR data is like the most amazing treasure map, not because we're looking for gold or statues,
09:20but because it allows us to ask bigger and better questions about what it was like to live at Angkor.
09:26The amount of detail that the LiDAR revealed about the landscape is absolutely mind-blowing.
09:31We were able to map an additional 20,000 features.
09:35The full scale of the city of Angkor is staggering, covering more than 150 square miles about the size of Denver.
09:46Hundreds of miles of roads and a complex network of waterways and canals connected the city.
09:53Hidden in the data were the keys to knowing how and where the citizens of Angkor lived.
10:00Because Angkor is built on a floodplain, all of the features were built on mounds.
10:05So when we're looking at the LiDAR data, we're not seeing ancient houses themselves,
10:10but we're seeing the mounds these houses were once built on.
10:13This is Angkor Wat, which is absolutely beautiful in the LiDAR data.
10:20So these are depressions and elevations in the land that we can very clearly see in this LiDAR imagery,
10:27but it's almost impossible to see these features on the ground because the vegetation is just so dense.
10:33All of these black dots are house ponds, and beside them are usually house mounds.
10:38Within the Angkor Wat temple enclosure itself, the LiDAR revealed more than 200 of these mounds.
10:46Using the LiDAR maps as a guide, Pipil Hang set out to investigate these sites on the ground.
10:52Those mounds are generally habitation sites.
10:56When we saw a similar pattern inside the Angkor Wat enclosure, we started to excavate those mounds.
11:04Turned out that those mounds have residential degrees, ceramics, Angkorian stonewares, and trade ware from China.
11:13So what we didn't know was those mounds were arranged into a grid system.
11:19That's when LiDAR came around.
11:25So here we are in the eastern section of the Angkor Wat enclosure.
11:29What I am standing on now would have been a house mount.
11:32And because of the overgrown, we can hardly tell the topographic change,
11:37but LiDAR map allowed us to pick up just a slight topographic change that allowed us to identify whether this area was mount upon to my right.
11:48The LiDAR data shows that we are standing in an urban block that is replicated into other urban blocks covering the entire Angkor Wat enclosure.
12:00You can tell when you're walking around that there's mounds there.
12:03It's really forested, but you can see that the landscape undulates quite a bit.
12:08Archaeologist Allison Carter has been collaborating with Papal to try to decipher what life was like at the Angkor Wat complex.
12:16The LiDAR in Angkor was incredibly eye-opening because you just see that they didn't just build Angkor Wat, which is a spectacular temple, right?
12:25Like they were transforming the entire landscape.
12:28And transforming it with extreme precision.
12:32If you look at the temple structures and align them with the gates of Angkor Wat, you would see that the grid system was actually aligned with the temple.
12:42It was all an engineered landscape.
12:45The remarkable urban design of the Khmer extended to the even larger royal complex Angkor Thom.
12:54You can see this is Angkor Wat. There's a huge moat that's very visible from the satellite imagery.
12:59And then up here is Angkor Thom. You can see the moat of Angkor Thom.
13:03But you really can't see all of that detail that becomes so clear and obvious in the LiDAR data.
13:10So you can just imagine when you enter Angkor Thom through these magnificent gates, it would have been a bustling city on either side of you.
13:20Again and again, the LiDAR revealed sprawling neighborhoods around Angkor's more than 1,000 temples.
13:27Combining this with the finds from excavations on the ground and new technologies, a team of archaeologists is finally able to crack one of the city's biggest mysteries.
13:39The size of Angkor's population at its peak around 1250.
13:45To answer that question of how many people lived at Angkor, we compiled all of the data that we had.
13:49C-14 dates, ceramic evidence from excavation, and we used some new cutting-edge algorithms and machine learning techniques to try to model the development of the city over time.
14:00I was part of a group of people that were working on trying to understand the growth of the city of Angkor.
14:07If you compare, this one is better.
14:09That one's better. It's a much bigger piece, yeah. So that'll be great to collect from this mound.
14:13That's a really good example of how we can bring in good old-fashioned, on-the-ground dirt archaeology with all of these new technologies.
14:20From our excavations, it seems like there's just one household or family per mound.
14:25We use ethnographic data then to estimate that there's about five people in a family.
14:30Another important piece of data was from inscriptions.
14:33A lot of the temples have foundation dates, and that was really important to understand when they were built.
14:39And inscriptions in two of the larger temples provide crucial clues about the population, which are of special interest to archaeologist Andrew Harris.
14:49They actually list the numbers of temple staff.
14:53These include government officials, dancers, laborers, and also how many people that the temple staff oversaw in the surrounding villages.
15:04Numbering between 200,000 and 300,000 for both temples.
15:08And then Sarah took that data, the LiDAR data, she used some machine learning algorithms.
15:13We brought this all together to try and create a model for how Angkor grew.
15:17The final estimate from their calculations was staggering.
15:21From our estimates, we think at its height that it had about 700,000 to 900,000 people living in the greater Angkor region.
15:27That would have made it one of the largest, if not the largest city in the world at the time.
15:32The discovery of Angkor's true size was a major breakthrough.
15:37But it was all the more impressive because of Angkor's location.
15:41Because the entire city was built on a water-soaked floodplain.
15:46Every year, the rainy season brings massive rainfall and heavy flooding.
15:52My family's connection with Angkor runs deep.
15:57During my childhood, my grandparents and my parents frequent the pagoda in Angkor.
16:04So I've been coming to Angkor since forever.
16:08Growing up here provides a different perspective on the water.
16:12We have the Great Lake to the south.
16:17The lake level changed drastically during the rainy season, particularly around October and November.
16:24The Great Tonle Sap Lake often quadruples in size in the rainy season, flooding vast areas of the countryside.
16:32In the dry season, nearly half the year, almost no rain falls.
16:37Why would the Khmer build in a place with such extreme swings between flooding and droughts?
16:43Water is incredibly important for the Khmer empire. Almost everything revolves around it.
16:48And one of the most important functions was irrigating the main agricultural crop of the empire, rice.
16:56The economy of Angkor was underpinned by rice agriculture, which is heavily dependent on a stable supply of water.
17:02There's a strong relationship between water, the floodplain, wet rice agriculture, and the early phase of Angkor period.
17:10As the Khmer empire and city expanded, controlling the flow of water was key for their economy, trade, and ability to feed a growing population.
17:21But how did they do it?
17:23Visible remnants suggested there had once been a complex water system.
17:28But it took LiDAR to reveal the full scope of the Khmer engineering.
17:33So with the LiDAR we were able to create this map, which very clearly shows the layout of the water management system.
17:39And how water flows into the city, through the city, and then how there are exit channels to remove excess water.
17:46The design was both ambitious and ingenious.
17:50A series of massive reservoirs called burais collected water in the rainy season.
17:55So here at Angkor we can see the large burais. Here's the west and east burais.
18:00And then all of these straight lines funneling into the city, these are man-made water channels.
18:07So this is rerouting water from northern areas of Cambodia into Angkor.
18:15The water was captured from natural rivers and moved into storage in these massive reservoirs.
18:20Those burais were really the centerpiece of the whole system.
18:24The largest burais stretched across more than six square miles.
18:29All of these features are so big that you can literally see them from space.
18:35That's the beginning of Angkor's power, water management.
18:40Those reservoirs are fantastically important.
18:43They hold huge volumes of water which can be distributed in the dry season.
18:46If you want a second crop of rice, for example.
18:49So it really kind of super boosts your productivity in those parts of Angkor which are downstream of those reservoirs.
18:55And the system extended far beyond the city itself.
19:00The landscape around Angkor is actually at a slight incline, about 1%.
19:05So the east and west burais can catch water as it comes into the city, hold it, and then redistribute it through the different channels.
19:12Taming the water was a major feat of urban engineering, with hundreds of miles of canals and reservoirs all dug by hand.
19:23But the floodplain also created a major challenge for an empire intent on creating monumental architecture.
19:31It's a bit of a difficult spot for building heavy temples like Angkor.
19:36So in order to do this they had some really ingenious engineering strategies.
19:41How did the Khmer manage to build massive stone structures on soft, deep soil surrounded by water?
19:48The first clue may be in the choice of building material.
19:52Hang Pao is the head of Apsara, the organization in charge of restoring the city of Angkor and the surrounding area.
20:01The priority of Apsara is about the conservation.
20:06How we can preserve the temple without falling.
20:10Before we start to make the restoration, we need to do research.
20:15The highly decorated walls of Angkor's temples are built of fine-grained sandstone, well-suited for intricate carvings.
20:26But appearances can be deceiving.
20:29Just under the ornate facade lies the first secret of Khmer construction.
20:35Hidden within the walls and foundation are blocks of a rough, porous stone called laterite that can be even lighter than sandstone.
20:44In terms of the web, it's less heavy.
20:51The core inside, they build in the laterite.
20:54And then they put the lampstone around for decoration.
20:58The whole temple is built in that concept.
21:01Using the lighter laterite greatly reduced the load on the soft ground.
21:08But the stone temples are still incredibly heavy.
21:11The stone that forms Angkor Wat, towering over 200 feet high, weighs millions of tons.
21:19And yet, it has survived the wet terrain for over 900 years.
21:26There must be more to the engineering.
21:29But what?
21:32Archaeologist Nette Simone leads restoration teams for Apsara.
21:37Her excavations are focused on understanding the key elements of ancient Khmer engineering.
21:43As a result of the excavation to see the condition of the foundation.
21:48I was able to understand the ancient techniques in building the temple.
21:55We observed that before shaping the temple itself, the ancient builders began by digging down to reach the natural soil.
22:04They then began compacting the soil inside.
22:09The next step involved filling the foundation with fine pink sand.
22:15This was followed by the laterite foundation.
22:18Above it, they laid the base layer using sandstone.
22:23As any trip to the beach reveals, dry sand is soft and shifts easily.
22:29While wet sand, closer to the water, holds firm.
22:33Water and sand together can create a solid base for construction.
22:38This could be one reason the temples at Angkor were surrounded by moats.
22:44Another thing that we can see is that all of these temples have water features around them.
22:48So each temple, which is marked in red, they tend to have moats around them.
22:53They build on the sand layer.
22:56And we understand that the sand layers need a lot of the humidity to make it stronger to support the load of the temple.
23:05The moats were, and still are, key to maintaining the required level of moisture beneath the biggest buildings.
23:12The water in the moats provide stability to the sand, which allows them to hold the heavy, heavy stone structures up.
23:21These innovations demonstrate that the Khmer were masters of hydraulic engineering.
23:27As to the hidden features that enabled Angkor's massive reservoirs, the burais, to function.
23:36Cambodian archaeologist, An Sopit and his team are excavating a unique location on the edge of the eastern burai,
23:44an ancient reservoir long dry and now covered in jungle.
23:49Right in front of me is the East Burai,
23:55a water reservoir from the Angkor era.
23:58These are the ruins of an ornate stone pier overlooking the burai.
24:03The Cambodian government hopes to restore the pier and partially repair the reservoir,
24:08to make it functional once more.
24:11The first step is to understand how both were constructed.
24:17But while excavating the pier and the reservoir wall, they found an unexpected surprise.
24:24At the excavation site I opened here, we found the foundation of the pier, made from laterite rock.
24:33Hidden beneath the wall of the burai is a laterite stone foundation extending more than 50 feet out into the reservoir.
24:41This work is important because it reveals a new discovery.
24:48We had never seen a construction with laterite sloping like this before.
24:53The next step is to determine if this massive foundation extends along the banks of the reservoir, beyond the area of the pier.
25:02We opened another excavation site 10 meters to the south and saw the structure continues with four more steps.
25:11But we only exposed a small section to confirm.
25:14In the future, we'll keep excavating to see if the laterite structure surrounds the water reservoir or end somewhere.
25:21No one knows yet how far this stone foundation extends around the burai.
25:30If this structure goes around a reservoir or part of it, it would be a new discovery for the Angkor area.
25:38The pier itself was a very special structure for Angkor's Hindu god kings.
25:45This pier was used by the king to offer alms at the temple located at the center of the eastern reservoir.
25:54In the middle of each reservoir was an island temple.
25:58The burais were more than just a brilliant piece of hydraulic engineering.
26:02Here's the East Burai and you can clearly see both in the mapping and in the lidar data that there's a huge temple in the middle of it.
26:09These large reservoirs were both functional and spiritual.
26:14The kings of the Khmer Empire played both a political and a religious role.
26:18In addition to being head of the army, the king was also a king god, so head of the religious system as well.
26:24Every king left an imprint of himself if he was powerful enough to create a mark on the landscape.
26:31Dozens of temples here are reflective of the absolute power over nature, over people, and over the landscape that they manifested during their reign.
26:44Over the centuries, rulers built larger and larger temples as the Khmer Empire expanded.
26:51Early in his reign in the 1100s, King Suryavarman II outdid all his predecessors, building Angkor Wat.
27:00Angkor Wat was a huge project. It would involve so many workers and so many craftsmen to be able to build it.
27:07Dedicated to the Hindu god Vishnu, nearly every surface of Angkor Wat was highly decorated.
27:14Traces of paint found on the carved walls and ceilings hint at its ornate history.
27:20All of the reliefs on the temples were originally painted in vibrant colors.
27:25Immense carved panels with scenes from Hindu texts run down vast hallways.
27:32Thousands of priests, dancers and attendants filled the temple and its grounds.
27:39It was a ceremonial center on a grand scale, demonstrating the glory of Vishnu and the power of the king.
27:49Temples were not just places of worship. The kings were also using them to demonstrate their power.
27:55So they probably were really acting as this kind of billboard for the king and the king's power and putting his stamp on the landscape.
28:03Wealthy and prosperous, the Khmer Empire was an attractive target for neighboring powers.
28:10Carved scenes at Angkor illustrate the story of one major conflict.
28:17In 1177, the nearby kingdom of Cham invaded Angkor in a surprise attack.
28:25To reclaim the city and restore power to the empire would take one of the strongest of the Khmer kings, Jayavarman VII.
28:35In the year 1177, the Chams conquered Angkor and occupied Angkor.
28:41Jayavarman VII made it his vow to reconquer Angkor.
28:46And part of this is depicted through various campaigns of warfare.
28:50This is probably the most elaborate of those campaigns and it involves a naval battle.
28:55What we can tell here is that one, it was intensive, it was violent.
29:00You could see the people falling overboard. Most of them have been stabbed or dead or whatnot.
29:05And a lovely crocodile eating a poor Cham who's fallen overboard.
29:09So through a series of campaigns lasting several years, he was able to eventually vanquish the Chams.
29:18With the enemy defeated and the Khmer back in power, Jayavarman VII would usher in Angkor's golden age.
29:26During his reign, he gave back to the public in many ways. He constructed hospitals and he built a number of different temples.
29:32This is a scene of a hospital. Here you have women giving birth, making medicine.
29:38This was a major point during the reign of Jayavarman VII. He built, I believe, 102 hospitals across the Angkorian Empire.
29:48Alongside his support of public health, Jayavarman carried on the tradition of his Khmer predecessors, monumental construction.
29:58When kings came into power, they all had specific mandates that they had to accomplish.
30:02And a lot of this revolved around temple building.
30:04Angkorian kings had an undocumented habit of trying to one-up their predecessors.
30:11If you think about Suryavarman II, he built the world's largest religious monument, Angkor Wat.
30:17Jayavarman VII left the largest architectural footprint on the Angkorian landscape of any monarch in Cambodian history.
30:25The pinnacle of his reign was the construction of Angkor Thom, an enormous complex more than five times the size of Angkor Wat.
30:35It is surrounded by eight miles of moat, and at its center stands a temple different from any built before or after.
30:44The Bayan. The Bayan is not a Hindu temple. Jayavarman was a Buddhist.
30:53All of the elite temples up until the reign of Jayavarman VII were considered to be Hindu temples of various deities.
31:01One of the most interesting things about King Jayavarman VII is that he switched the state religion from Hinduism to Buddhism.
31:08Hindu worship involves a pantheon of gods and observation of rituals set out in the Vedic scriptures,
31:15while Buddhism focuses on enlightenment through the teachings of the Buddha.
31:20The Bayan temple towers feature 216 enigmatic faces that may contain a hidden secret.
31:29The faces on the Bayan in the gate are potentially a Buddhist saint or they're the king himself.
31:35And the reason we think it's Jayavarman VII himself is because a number of the images that we know of Jayavarman VII
31:44look almost identical to the face towers on the Bayan and on the gates.
31:48Following the reign of Jayavarman VII ending around 1218, Angkor was at the height of its size and influence.
31:56What was life in Angkor like at its peak?
31:59Few written descriptions have survived from the Khmer, but historians have one detailed account.
32:04In the 13th century, the emperor of China sent an emissary to Angkor.
32:09Joe de Guan was ambassador of Mongolian-controlled China to Cambodia.
32:16He lived in Angkor sometimes between 1296 and 1297, almost one year.
32:22Joe de Guan left us a journal and it's incredibly valuable in terms of the types of details that he wrote about.
32:28I'm not sure if he intended for archaeologists to read this, but it sure provides a lot of information.
32:33Around the outside of the city walls, there is a large moat.
32:38The walls of the bridges are made of stone and carved into the shape of snakes.
32:43As an archaeologist, I refer to Joe de Guan constantly.
32:47He talks about how poor people lived in smaller houses and their roofs were made out of thatch,
32:52but richer people would have bigger houses and their roofs would be made with ceramic roof tiles.
32:58Joe de Guan's journal described scenes of everyday life.
33:03Their litters are made of pieces of wood that bend in the middle.
33:07A person sits in the cloth and is carried by two people, one at each end.
33:12The parasols are made of a strong, thin, red Chinese silk.
33:18But how reliable are Joe de Guan's descriptions?
33:22His descriptions of daily life are actually backed up by a lot of what we see on the walls of the Bion Temple.
33:31Joe de Guan describes Angkor as a bartering system and he describes a market day.
33:37He describes how merchants, mostly women, would lay down their blankets and sell their wares.
33:45The local people who know how to trade are all women.
33:49Small market transactions are paid for in rice or other grain and Chinese goods.
33:56Larger in size are paid with cloth.
33:59There's these bas-reliefs of people cooking and eating food.
34:03And then in our archaeological excavations, we find really similar materials.
34:07When we are excavating an occupation area and you're like,
34:11Oh, this looks just like what's on the Bion.
34:13Like, you can really see how these different sources of evidence come together to give you a more complete picture of the past.
34:19That record represents a fantastic contribution to our understanding of the life of the city.
34:23And at that time, the king and the court were very impressive.
34:26The city was enormous and there was clearly a lot of wealth floating around.
34:30Above the gates are stone Buddha heads.
34:33One of them is decorated with gold.
34:36In the center of the capital is a gold tower.
34:41Joe de Guan describes Angkor as a very active, very vibrant metropolis.
34:46He talks about the significant amount of wealth coming out of the palace.
34:49So Joe de Guan described the temples at Angkor not as these stone mounds that they are today,
34:58but covered in gold and very clearly upkept.
35:01But that upkeep would not last much longer.
35:05Joe de Guan's record represents the very kind of last gasp of Angkor as a spectacular, opulent, thriving metropolis.
35:14From that point forward, things change dramatically.
35:17This inscription indicates that this temple was the very last Hindu temple that was dedicated at Angkor.
35:32We actually have an exact date for it.
35:34It's the 28th of April, 1295 CE.
35:38Which was just a year before Joe de Guan showed up.
35:41As far as we know, there are no temples after this one.
35:45As the 1300s continue, Angkor starts to decline.
35:52We start to see evidence from different sources that population starts to slide.
35:57There are no more inscriptions created, no more temples built.
36:00Official written histories of the Khmer did not appear again until much later.
36:06There's a bit of a black hole in the historical records from about the 13th century to the 15th century.
36:13So it's a big gap. It's many hundreds of years.
36:16What happened to bring an end to centuries of prosperity and monumental construction?
36:22No big city like this one is ever going to have a single reason for its start or its end.
36:27So in that context and in the complexity of that story, we can start to accept that there's no linear, simple, single explanation for the demise of a place like this.
36:35But rather a tangle of different explanations that happened to Karawales at a particular point.
36:40The warm and humid environment of the Cambodian jungle works against the archaeologists trying to shed light on the declining years of Angkor.
36:50The rainforest does not help because almost every wooden remain and the vast majority of structures at Angkor were built in wood deteriorate very, very quickly.
37:02One of the most puzzling aspects of Angkor today is the complete absence of human remains.
37:09No bodies, no burials.
37:12This is a very fascinating thing that's baffled archaeologists for a long time.
37:16There are no funerary remains until much later.
37:21So for 600 years, one million people, not a bone, not a cremated remain, not a funerary jar, not a trace of a funerary remain.
37:35The lack of bodies, human remains in Angkor's archaeological record is fascinating and frustrating in many ways.
37:45It's very rare for a city which had 700,000 million people in it, that there are so few bodies.
37:52What happened to the bodies of the ancient Khmer?
37:55With Chodakwan, he talks about different burial practices.
37:59The body is taken to a remote, uninhabited spot where it is thrown down and left.
38:06After that, the vultures, crows and dogs come and eat it.
38:12But the archaeologists at Angkor are struggling to find the location of the sky burials that Chodakwan described,
38:19where the dead are left to the elements and animals.
38:22He said that they carried the dead outside of the Uncle Tom Gates and then left it outside the wall.
38:29But when we look at LiDAR data, outside the wall would have been just settlements everywhere.
38:34Where was that outside the wall?
38:37Burials do tell us a lot about health and the individuals.
38:42So to find a graveyard, or even to find cremated burials, that would be phenomenal for encoding archaeology.
38:49But so far, we have not found evidence of a burial ground yet.
38:56Without the bodies themselves, archaeologists are searching for other clues, hoping to find out, when did everyone leave?
39:06Dan Penny is focusing on the burials and canals, and the sediments below the surface.
39:13The sediment is accumulating at the bottom of these reservoirs, ponds and so on.
39:18They end up as beautiful little traps for material, landing on the surface and then settling onto the sediment.
39:25And then being buried by subsequent layers of material.
39:28And so it goes, layer upon layer.
39:31We can come along hundreds, sort of thousands of years later and take these samples and find this undisturbed material,
39:37which faithfully records the conditions that were occurring when they were deposited.
39:41The moats of Angkor Thom are a fantastic archive.
39:44They've been largely left alone, so we can use them as natural archives of change through time.
39:51This core goes all the way back to pre-Angkor.
39:58So it goes into the alluvial soil beneath the moat, and we get the whole sequence all the way through the rise and fall of Angkor and into the modern day.
40:08After processing, Dan studies the samples from the sediment layers under a powerful microscope.
40:14So this guy here is a pollen grain from a lotus.
40:19This one is a sedge, so it's another aquatic plant.
40:22It's a huge chunk of charcoal coming out of maybe a domestic fire, someone's fireplace where they're cooking.
40:27Could be any source, but it's invariably associated with people.
40:30Radiocarbon dating adds another layer of information.
40:34Most of the work that I do with radiocarbon is actually based on dating the pollen grains themselves.
40:39Each of these pollen grains is about 10 to 20 micrometers in diameter.
40:45A micrometer is a thousandth of a millimeter, so they're pretty small.
40:50The types of pollen grains, found at different depths in the core,
40:55can reveal when the ancient moats were well maintained or filled with weeds.
41:00When moats are being maintained, you'll often see species rooted into the sediment at the bottom of the moat,
41:05as opposed to an unmaintained moat which is kind of completely covered by ferns and grasses and other things.
41:12Once management stops, the moats will quickly cover with vegetation.
41:16We definitely find evidence of the water systems not being maintained.
41:21Once they're abandoned, they are permanently abandoned,
41:24and so that represents a very clear horizon for us to say,
41:26hey, at this point, this water feature is no longer being managed.
41:30What we are finding increasingly from a range of different variables, charcoal among them,
41:35pointing to a progressive decrease in the intensity of occupation in the very epicentre of Angkor as a city,
41:41all of these things are decreasing progressively through the 1300s.
41:46What could have happened at Angkor in the mid-1300s that would have caused the Khmer to leave?
41:53And the reality is that we don't really know what happened.
41:56There are a number of different hypotheses, and probably it was a combination of all of them.
42:00So we need to cast our mind to what other reasons might there have been for people to start leaving Angkor.
42:06There's another story there, sitting underneath, which is far more interesting and far more important.
42:11Angkor was not the only place to suffer a major population decrease during the 1300s.
42:18The bubonic plague, also known as the Black Death, that killed millions in Europe, came out of Asia during this century.
42:26The timing fits the abandonment of Angkor, but is there any evidence of a connection?
42:32Evidence of a pandemic at Angkor would be revolutionary.
42:39The effect of a pandemic in a pre-industrial city like this one, which was massive and had a huge population,
42:45would have been catastrophic, and it would likely have led to very rapid depopulation,
42:50particularly by those people that can move.
42:53If there's evidence of a pandemic, I can assure you there will not be.
42:59Because if you have a pandemic here, you will find bodies, right?
43:05Because there are 900,000 people here at the peak.
43:09If you have the plague here, it would have been horrific,
43:12and there would be no way that people would have been able to deal with that much human remains in the normal way.
43:19If it wasn't a cataclysmic event, could a slow decline have been triggered from within the Khmer Empire itself?
43:30What changed for the Khmer?
43:36A discovery during the restoration of Angkor's Tha Pram Temple may provide a clue.
43:43Tha Pram was constructed as a Buddhist temple in honor of King Jaya Varmin, the seventh late mother.
43:54The first step taken by our team was to conduct an initial survey.
43:59Our team discovered broken pieces of a Buddha statue.
44:05Once our team began digging and cleaning, more and more of the statue began to emerge from the ground.
44:14More than 140 pieces in total.
44:18Some of these sculptures were buried, while others were left scattered around the temple grounds.
44:24Pha Pram was not the only temple to see this kind of destruction.
44:33So we are at Priya Khan Temple here.
44:35It was dedicated in the year 1191 to Jaya Varmin VII's father.
44:40What's on the left here is a series of niches where the Buddhas have been completely hacked out,
44:45and we think that this was an act of religious violence.
44:48What would have caused the Khmer to turn against Buddhism?
44:52We believe that in the 13th century, one of Jayavarman VII's successors, Jayavarman VIII, was responsible for this
44:58and shifted the royal cult from Mahayana Buddhism back to Hinduism.
45:02This act was either due to religious reasons or even political reasons as a retaliation against the reign of Jayavarman VII.
45:10After Jayavarman VII's golden era under Mahayana Buddhism
45:15and Jayavarman VIII's Hindu backlash, the Khmer religion changed one last time
45:22to an older form of Buddhism called Theravada Buddhism.
45:27The Khmer Empire was undergoing another major cultural and religious shift.
45:34King Njavarman III essentially switched the entire religious ideology and landscape to Theravada Buddhism
45:42beginning during his reign in the year 1296.
45:46Chinese ambassador Zhou De Guan arrived at Angkor just as the Empire moved to worshipping
45:53at Theravada Buddhist temples called Viharas.
45:56Zhou De Guan saw this society that was in transition and changing.
46:01Rather than more temples being constructed, it was now Vihara and monasteries.
46:06There were still construction activities after 1295.
46:11The type of structures, the type of temples, changed because of Theravada Buddhism.
46:17The Theravada Buddhism only required a terrace surrounded by a boundary stone
46:23and the Buddha statues and then wooden upper structures.
46:28So that's very simple and that's what could drive a lot of change.
46:32The age of giant ornate stone temples was over.
46:36The shift away from huge temples and elaborate ceremony not only meant less construction,
46:42but fewer monks, dancers and religious staff.
46:46All this could have contributed to a shrinking population at Angkor in the 1300s.
46:52But would it have caused the Khmer to completely abandon such a vibrant city?
46:58Or was there another fatal blow to Angkor?
47:02We don't obviously have a historical record of climate from Angkor.
47:06There was nobody here recording it at the time.
47:08So what we have to do is look for other sources of information that can tell us that.
47:12We exploited some tree ring records from the mountains of Vietnam that tell us about rainfall in particular.
47:20And they tell us a really interesting story about variations in weather and climate during the period where Angkor is abandoned.
47:28The study showed a series of droughts at a time when Angkor was vulnerable.
47:34So those two droughts occurred from about the middle of the 14th century, from about 1350 onwards.
47:41And they lasted for about two decades, more or less, at a time.
47:44So they were really, really severe, quite profound, nothing like we have seen in the modern era.
47:50Angkor had survived droughts before, but this time may have been different.
47:56So you have the sense that Angkor is very successful, but it's building itself into a state of precariousness.
48:02So by the time it gets to the middle of the 1300s and you're hit with a massive drought,
48:06and then a big wet period and another massive drought, the whole system starts to crack and come apart.
48:11Fractured it, shattered it by eroding, by sedimenting or infilling canals,
48:17blowing up banks and reservoirs, doing all sorts of damage to the system.
48:22You need to have the people who continue to have that knowledge.
48:26Without those people, everything collapse.
48:28The LiDAR data also reveals some failures in the water management system.
48:33So here we can see where a channel cut through an embankment.
48:37You can see that this is going right through the middle of a densely occupied urban space.
48:42So this would have been devastating for the people that were living here at the time.
48:46And one of the other things is we can see that this failure was never repaired.
48:50At some point in the 1400s, the city of Angkor was largely abandoned.
48:56Only a handful of farmers, monks and religious pilgrims remained.
49:01Over time, the jungle covered the ancient heart of the Khmer Empire.
49:07For over 600 years, the seasonal floods and droughts ravaged the ancient monuments.
49:14Today, Cambodians have an ambitious plan.
49:17Restore the ancient hydraulic systems and bring the water back to Angkor and the surrounding area.
49:23Our ancient ancestors already designed and built working water systems.
49:31So as the younger generation, our work is simply to restore and rehabilitate.
49:38We are combining the use of ancient technology that already exists with our modern technology.
49:48We are now able to restore and rebuild the city of Angkor.
49:49We are now able to restore.
49:50We are now able to restore.
49:51Restoring the channels into the burais to prevent flooding and hold water has been successful.
49:55The northern burai is now full.
50:00So is the west burai, holding more than 13 billion gallons of water.
50:06The project to widen the canals and fill the ancient moats continues.
50:16Including work on the moat around Angkor Wat.
50:21Angkor's legacy reaches beyond Cambodia.
50:44Angkor is a location.
50:49It's also a representation of a culture and a civilization.
50:54The ways in which humans can flourish in difficult environments.
50:59It represents a celebration of the past and it represents a warning to our future.
51:04But for the Cambodian people, the centuries of history at Angkor form a central part of their identity.
51:12Through the transition from the Angkorian to the post-Angkorian period, it's social transformation.
51:19After the collapse of Angkor, it became a symbol of power.
51:24For the Khmer people, Angkor is an important cultural symbol.
51:32A reflection of the Khmer identity and soul.
51:39All the local people want to pay the respect to Angkor.
51:44Angkor, for the Cambodian people, is a lot. Everything.
51:51The sacred aspect of Angkor, I never left Angkor. It's still here.
52:03It's still here today.
52:04It's still here today.
52:05It's still here today.
52:10The
52:11The
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