Transcription
[Music] It's tiring. The wind's blowing. It's, it's icy cold. This is so steep. I don't know how they got the bricks up here. The Great Wall of China. Wow. It's like being on top of the world.
[Music] Endless wall, endless watchtowers, all the way to the horizon. It's like nothing you could ever imagine. It's been studied for decades, but now new technology is revealing its secrets like never before. I'm Alan Maca, an archaeologist and expert in ancient civilizations, and I'm going to investigate China's distant past from a whole new perspective. Space. Today, state-of-the-art satellites see the world in stunning detail and reveal hidden archaeology, enabling us to recreate a lost ancient world invisible to the naked eye.
[Music] Working alongside leading Chinese experts, my team and I will travel to some of the country's most remote and incredible landscapes and, with cutting-edge science, investigate previously unknown cultures, lost cities, and devastating cataclysms. This is ancient China as you've never seen it before. Just outside China's capital, Beijing, 10 million people a year come to marvel at the Great Wall. This is the biggest man-made structure on the planet. But the only way to really see just how vast it is is from 500 miles above the earth. Using satellite images, I'm going to track the Great Wall across towering mountains and remote desert, exploring massive defenses. They will just start raining down fire and arrows from above. Meeting archaeologists as they unearth its ancient past. Oh, this is amazing. You've literally just found these. And revealing its long-hidden secrets. Looks really cool. To discover if this great monument could be even bigger and far older than we'd ever thought before. I'm starting my mission 70 miles north of Beijing in the rugged mountains of Jin Chandling, at a part of the wall that's remained unchanged for hundreds of years.
[Music] You see pictures of the Great Wall in tourist books, but this is something else. Out here in Jin Chandling, satellite data shows how the wall crosses seemingly impossible peaks. And every few hundred feet.
[Music] Huge stone structures on the ground. These towers reveal meticulous engineering.
[Music] Look at how beautiful this is. Really formal arches here. Lots of space. Windows all the way around. You have a 360-degree view over the landscape. It's incredible.
[Music] This is just one of around 25,000 watchtowers built by the Ming Dynasty, who ruled China from 1368 to 1644. Between the towers, ingenious defenses. I'm seeing these strange holes along the wall that open to the outside. What they would have done is taken about a five-pound rock, hollowed it out, stuffed it with gunpowder, put a wick in there, and literally just rolled it out the hole. And no more invaders. The Ming went to these extraordinary lengths to combat a mortal enemy.
[Music] From space, satellites reveal vast grasslands to the north of the wall. Wild enough today. In the days of the Ming, this was home to tribes of nomadic horsemen, the Mongols. These fearsome warriors had been attacking and pillaging China for centuries. The Ming built the Great Wall to keep them out. Now, 600 years later, Chinese experts are using science and technology to reveal its secrets. Everywhere I look, I see watchtowers on the top of the mountaintops. Near a remote section of the wall, this view is unbelievable. Canadian archaeologist Sarah Klassen is on her way to meet one of the teams carrying out this groundbreaking work.
[Music] Li Jia and Professor Zhang from Tianjin University are using drone data to create a 3D model of the entire Ming Dynasty wall. It's the most complete scan ever attempted. We have covered two thousand one hundred kilometers along the Ming Dynasty wall. We still have two thousand five hundred kilometers to cover. It's a huge job.
[Music] Without this technology, doing something like this would not be possible. Just look at the landscape. You'd have to scale up all of those cliffs and map all of these features. It would take decades, if it would even be possible at all. The new scans reveal the incredible achievements of the Ming in some of China's most extreme terrain. Even on completely impassable ridges, they still succeeded in erecting towers. Can you show me what you've done here? You can see there is the rampart here, very close to the cliff. They want to stop all the enemies. And a lot of parts of the Great Wall follow the ridge. And within the scans, new discoveries.
[Music] Li has spotted mysterious openings along the base of the wall.
[Music] Using his data, I'm heading 120 miles east to investigate. Look at this rugged landscape. And check out this ridge. See the watchtowers up on the ridge? That's where the wall is. So the wall is snaking all the way down to the saddle over here, and that's where I want to go. The wall here is crumbled away, but originally it would have stood as tall as a three-story house. Wow. Can you imagine a solid wall all the way down from this ridge? And all of a sudden, there's this door clear through to the daylight. It's completely baffling. Why would a defensive wall have a doorway running right through it?
[Music] Yeah, this is a pretty small, compact space right now. But without all this rubble here, this would have been the size of a person. Would have just walked right through here. The crazy thing is, you know, this is not some random hole in the wall. This thing is incredibly well built. Look at all these bricks. This is a perfect, beautifully made arch. So this was planned. And the question is, why? Li Jia has found more than 50 of these doors along this part of the wall. And it's thought that they could be used by scouts sent out to spy on the enemy. But the data is revealing something else. The ragged edge revealed in this scan isn't a decayed doorway, but the entrance to a hidden tunnel that was once bricked up before being smashed open. Looks really cool. The doctor, the hidden door, somebody called the secret door. This new discovery is completely different from any of the other openings Li Jia has found, potentially a way of launching a sudden attack.
[Music] It seems this hidden door is originally sealed by normal bricks. Soldiers inside then break the surface and go outside and launch an attack. Smashing open this thin layer of bricks allowed the Ming forces to ambush the enemy. Before Li Jia's discovery, experts had no idea these hidden tunnels even existed. It's an incredible find. We cannot imagine that before. You know, all this makes me astonished. The latest technology is revealing that the wall is far more than a simple barrier. It's a complex military system. The big question is, just how far does it stretch?
[Music] Using satellite images, we can reconstruct how the Ming wall extends far to the west, from mountain ranges, through wild grasslands, and into barren desert, right to its end. Where the Ming stopped building here, at the very furthest reaches of their empire. A huge construction, far greater than any of the thousands of towers along the way. What is it? And what was it for? To find out, I'm going to follow the wall to a far-flung corner of western China.
[Music] I'm investigating the secrets of one of the world's greatest ancient icons.
[Music] Using satellite data, I've tracked the Great Wall all the way from the mountains east of Beijing to the Gobi Desert, a 500,000 square mile expanse in the far northwest of China.
[Music] Just over here, I can see sections of the wall. The feat of engineering required to build something so far out here in just this barren, desolate environment, just kind of boggles the mind. After hours following the wall, something massive emerges from the desert haze: a mighty fortress. Today, the modern city of Jiayuguan is nearby, but 600 years ago, this fortress would have stood alone in a desolate wilderness. I never imagined I'd ever see something like this, all the way out here in western China. The Great Wall terminates in the mountains just a few miles south of here, making this incredible structure the wall's final gateway, the last fortress at the furthest edge of the Ming Dynasty's vast empire. Look at how massive this is. This rivals any, any gate or battlement anywhere in the world at this time. Here, you really get a sense of the ambition, the engineering, and the immense power of the Ming. A deep moat, walls up to 36 feet high, and watchtowers on every corner form three layers of defense. And even if the enemy does make it inside, there are traps designed to create devastating kill zones. You walk into this courtyard, and if you're an invading army, they can close those doors, close those iron doors, and you're trapped here. And all of a sudden, they will just start raining down firing arrows from above, and your invading force is doomed. This is an ingenious military strategy, all set and fixed in the design of this incredible fortress. It's massive, but also meticulously built. The precision of construction here is amazing. And, you know, the emperor demanded that. And there's this legend that says the architect told the emperor, he said, "I can tell you the exact number of bricks it will take to build this fortress." He said, "It will be 99,999." And incredibly, at the end of construction, there was just one brick left. And that brick is set over there on that little ledge as a kind of mini monument to the incredible precision design of this fortress. Its position right at the end of the Ming Dynasty's Great Wall earned it the name, "The First and Greatest Pass Under Heaven." But this fortress is just one small part of a mega-structure like nothing else on Earth.
[Music] Just one end of their Great Wall of China.
[Music] Until we had images from space, experts didn't know how massive the Ming Dynasty's Great Wall really was. But now, Chinese experts have calculated it's five and a half thousand miles long. That's over 1,500 miles more than previously thought, and long enough to stretch from New York to Los Angeles and all the way back.
[Music] Again. But new technology is also unearthing secrets that take us beyond the great empire of the Ming. 1,200 miles away, Sarah has set up a base camp in the shadow of the Great Wall. We know the fortress of Jiayuguan marks the end of the Ming Wall, but the satellite data reveals something else. Oh, wow.
[Music] Chinese experts have told Sarah about another section even further into the desert. If I zoom in on the satellite imagery, I can see that this part of the wall is much more eroded than other parts of the wall. So I might suggest that it's older than the parts of the wall built during the Ming Dynasty.
[Music] This wall stretches far beyond the Ming fortress, continuing west for hundreds of miles. The wall is completely straight in the middle of this desert. There's absolutely nothing else around here. Can't imagine why they would need to build a wall here. So what's going on? I'm heading west in search of answers. I want to know just how old is this wall.
[Music] Where does it go? And if the Ming didn't build it, who did?
[Music] I'm now more than 230 miles west of the fortress of Jiayuguan.
[Music] Here in the Kumtag Desert, it's one of the harshest environments I've ever been in my life. You know, very little grows here. The temperatures are literally below freezing. It's a hell of a place to imagine finding archaeology. Sarah's guiding me to faint traces of what looks like an even older wall that she spotted on the satellite data.
[Music] If I get up here, I think I can get my first glimpse. Wow, this is cool. And it's not exactly what I expected.
[Music] And it looks kind of primitive. Want to see more? Let me get up closer here. In the middle of nowhere, a stretch of ancient wall, and it looks very different from anything I've seen so far.
[Music] This is a very distinctive kind of material. We have rammed earth, packed down with a reed foundation. These are reeds. This is actually a, you know, a type of thick grass pressed in there to serve as a foundation to hold the wall stable. This framework is an ingenious way of building, even with the desert's loose sand and gravel. But if the Ming didn't build this, then who did? To find out, I'm meeting Zhang Junmin, the head of a team from the Gansu Institute of Relics and Archaeology, who are digging for answers. Wow, this is so cool. Tell me, what do you have here? These are two arrowheads we found nearby. One is bronze, and one is iron. You can see it's still sharp. I've never seen this shape to an arrowhead before. You know, where it's, it's basically three-sided like this. And is that common? I found lots of these along the wall in this area. These arrowheads are very typical of the Han Dynasty. Fifteen hundred years before the Ming, before the Roman Empire formed in the west, and Cleopatra ruled ancient Egypt, the Han Dynasty rose to power.
[Music] They oversaw a golden age of art, culture, and economic prosperity. They're so well preserved. I'm just amazed. Look at that edge. It's just incredible. The form is just so clear and beautiful. These tiny arrowheads reveal something momentous: that the wall here is more than 2,000 years old. It's an even earlier Great Wall of China that once stretched for over 6,000 miles.
[Music] Much of the famous Ming Dynasty wall was simply built right on top. 1,500 years later, battered by desert winds for over two millennia, what remains of this ancient stretch of Great Wall are just fragments of what was once a mighty barrier. It's kind of hard, just looking at these ruined sections of the wall, to get a sense of what it looked like originally. So, using historical sources and archaeological evidence, we've made this pretty phenomenal digital reconstruction of what the wall might have looked like. It's just amazing. When it was first built, the wall would have stood up to 20 feet high. This thing was enormous. I can only imagine being part of an invading nomad army and coming up against this wall and thinking, you know, maybe it's better to just go home, because this was formidable.
[Music] Then another discovery, just unearthed from the desert sands, that suggests the wall was about more than just defending Chinese territory. We found this coin nearby. It's a Wu Zhu coin. Oh, this is amazing. You've literally, literally just found these. Yeah. May they have been left here by merchants. These merchants may have been traveling along a series of ancient trade routes known as the Silk Road, established by the Han. The Silk Road stretched from China through Central Asia and India to modern-day Turkey, Egypt, Arabia, and Rome. It brought huge wealth to China and had to be defended at all costs. So the Great Wall was not just about protecting the empire; it also served to protect China's gateway to this vital artery of global trade.
[Music] But there's something else intriguing here, alongside the wall. More ancient remains.
[Music] Rising from the desert, a mysterious eroded structure. My tech team, Ryan Castner and Eric Lowe, are joining me, and working with experts from Peking University, we're going to investigate.
[Applause] I'm on a quest to uncover the secrets of the Great Wall of China.
[Music] And my tech team is working with researchers Ma Li, Wu Yunnan, and Ma Qinglong from Peking University to investigate what seems to be a mysterious tower built near an ancient section of wall. So they're flying the drone now. We're going to first do sort of a lawn mower pattern over the top to get the aerial view of the tower there. The drone takes hundreds of images of the structure, which we'll combine to make a detailed three-dimensional model. After that, the team will scan a four-mile section of the wall for traces of any more remains. Using a drone to be able to fly will save us a lot of time. The drone can go a lot faster than we can on foot.
[Music] Hours of flight and 1,500 individual pictures later.
[Music] Hey guys, come on in. And I've come to check out the results with archaeologist and leading Han wall expert Yang Jun, who'll help us interpret our findings. All right, guys, so show me what you got. All right, so to give you some context, you can see the wall from, from the satellite image very clearly. If you look, it's a nice linear feature here. But switching to the 3D elevation model reveals details not visible in the satellite imagery. So if we look, and actually in this spot here, um, right where it bends there, there seems to be a clear, clear bump there that doesn't seem to be natural. You can see in the elevation model, the redder it is, the taller it is. That's a five or six meter tall mound there. It seems to make a whole lot of sense to us that that would be another tower because it turns at an angle. It cuts back south. Exactly, exactly. So that would be a natural spot where you'd want to look out to see on all sides where everything was. The structure's height and strategic position suggest it may have been a watchtower. Then Ryan spots something totally unexpected. You can see a clear structure, another tower that was behind the wall, basically on top of a hill. This is really interesting. Did they build towers off the wall? From our research, we found most of the towers were along the wall, but there are a few that are outside it. It's bizarre. Some of these towers are deep in enemy territory, miles beyond the wall. Were they really just simple watchtowers, or could there be more going on here?
[Music] 600 miles away, in a vault at the Gansu Jianju Museum, are ancient relics which could hold the answer. Research director Sao Song Li has agreed to show our historian, Dr. Chao Hue Chenille, these amazing finds. These are wooden slips. They're about the length of a ruler. The wood looks well preserved. On it, you have these writings in ink, very fine writing. Buried in the desert for 2,000 years, these slips were unearthed in what was once the office of a military commander, and they contain instructions for soldiers stationed at the towers. Okay, they're really hard to make out. Oh, first of all, on the very top, there is one dot that tells you that's the beginning of the rules. And then the first two characters are "Xiongnu," that means the Huns. The Huns were feared nomadic horsemen who roamed the northern grasslands a thousand years before the Mongols. So the rule here is talking about what you should do when the Huns come into the border. Okay? So the next characters say, "You must raise a flag on the pole." Raising this flag, a marker known as a pung, could only have one purpose: to signal other towers. And there are even rules for what to do at night when flags can't be seen. "By night, start a fire on top of a tower and do not put it out until the morning. All towers that see this light should also light, and it goes all the way down the defense line until it reaches the commandery where the soldiers are."
[Music] Said. And the slips even contain instructions on how to signal how many enemies were attacking. So let's say you have more than a thousand Huns, and that's what they've sighted. There's a very specific signal that they must send, so that without words, the commander would know that there are a thousand riders coming towards us. This tells us the towers we've mapped in the desert, including those deep in enemy territory, are not simple watchtowers. They're beacon towers, part of a complex early warning system.
[Music] Using our drone data, we can now reconstruct a complete 3D model of what they may have looked like. Built over 2,000 years ago, they were made of rammed earth, clad in plaster, and stood up to 26 feet high, with platforms on top where the fires were lit. And thanks to the incredible insights revealed in the wooden slips, we now know that these towers formed a sophisticated communication system designed to provide early warning of an attack and pass it for hundreds of miles along the wall.
[Music] What the Han created is remarkable. But were they the first to build a defensive wall to protect their empire? To trace the wall back to its very roots, I need to travel even further back in time, to the reign of a tyrant of unrivaled power and ambition, the man who conceived of another of ancient China's greatest icons.
[Music] The Terracotta Warriors. I'm in the city of Xi'an, having traveled over a thousand miles from the deserts of the far northwest. This was once the ancient capital of China. I want to trace the origins of the Great Wall, but to do that, I need to go back in time to the formation of China itself and explore the story of China's first emperor. I'm starting out with his most famous.
[Music] Creation: the Terracotta Warriors.
[Music] I've been reading about this for years and years, but this is my first time here, and I'm telling you, nothing, nothing prepares you for this experience. This is literally one of the greatest achievements in all of ancient civilization anywhere in the world. More than six thousand figures, row upon row of soldiers and commanders, an entire army immortalized in clay. And all built for the first emperor of China, Qin Shi Huang Di. From where I'm standing, there are no two figures that are alike. The uniforms are different, their facial expressions are different, right down to the mustaches. This tells me about the power that the emperor was able to summon in his lifetime as a ruler. This is extraordinary. From space, we can see that the huge hangar that shelters the Terracotta Army is just one tiny part of his massive mausoleum complex. And at its center.
[Music] Is this hidden within this strange-looking hill is the emperor's tomb. It's never been opened. Archaeologists don't yet know how to excavate it without destroying the contents. But I'm meeting Dr. Zhang Wei Xing, who's been using seismic scanning technology to glimpse what lies beneath. What do you know about what's in there? We knew there's a huge burial chamber under the earth. It's 160 by 140 meters in size. The 30 meters. And within that, there's a huge nine-level platform. Ancient texts say the tomb contains a replica of the cosmos with pearls as stars, rivers of liquid mercury, and even deadly booby traps. It sounds far-fetched, but Professor Zhang has found evidence that suggests there may be some truth to the legends. We detected very high levels of mercury in the air, so we know there is mercury inside the huge burial chamber. Holy smokes.
[Music] These findings suggest there's truth in the ancient texts, and that means there may also be truth in what they record of another of the emperor's construction projects: a huge defensive wall, the first Great Wall of China. Though little remains today, the records show it stretched for nearly 2,000 miles across northern China. They also reveal the human cost of the emperor's ambition. He forced 300,000 soldiers and half a million laborers to work on its construction, and for many, it was a death sentence. They died of starvation or fatigue, or in some cases, they were flogged to death. But it cemented Emperor Qin Shi Huang Di's place in all of world history.
[Music] After an incredible journey spanning thousands of miles and reaching far into the past, I'm nearing the end of my quest. But one intriguing mystery remains: Did the first emperor really conjure up the idea for a Great Wall right out of thin air? To find the answer, I need to go back even further, to a time before his bloody rise to power, and before the formation of China itself. I want to investigate one final mystery surrounding the Great Wall of China: Just how did the first emperor get his idea to build a colossal defensive wall? That question has taken me 300 miles north of Xi'an to the Loess Plateau. I'm following satellite images to mysterious lines of rocks and steep earth banks, the remains of a primitive and clearly ancient wall. There's pieces of pottery scattered all over here, all around. Clues to who built it. I mean, this piece is just a commoner, commoner like cooking jar. And the designs on the outside tell me this is very early. We're talking about pre-Qin Empire, 2,200 years ago. At a time before the first emperor came to power, China was divided into seven warring states. To protect their territories, each state built their own defensive walls. Incredibly, these are the remains of a wall built before the formation of China itself. This is pretty cool. In 221 BC, the king of one of the warring states, Qin Shi Huang Di, is waging bloody war. He crushes all other states, unites China, and declares himself the first emperor. With his newfound power, he combines the warring states' existing walls and builds new stretches to create one huge defensive shield over 3,000 miles long: the first true Great Wall of China. His incredible construction would be extended and developed by the Han Dynasty, and over a thousand years later, the Ming Dynasty would take things even further, creating the monument we see today. The Great Wall was not one single thing. It was a mesh of many walls that span huge periods of time. I mean, truly, China is defined by its walls. My investigation has taken us right across China to the edge of empire.
[Music] I've tracked the Great Wall back to its very roots, more than 2,200 years ago.
[Music] And revealed how it's not one wall, but many that evolved over the centuries into an astonishing military masterpiece. We always knew it was big, but now, using the latest satellite imagery and cutting-edge technology, Chinese archaeologists are revealing that this world icon is even greater than we ever imagined. It's more than twice as long as previously thought, spanning 13,000 miles long, enough to stretch halfway around the Earth.
[Music] On this journey, I've learned that the Great Wall was as alive and dynamic as the generations of people who built it. It's the result of struggle and achievement, spanning more than 2,000 years. It's not just an enduring symbol of ancient China; it's the story of China itself.
[Music] You.