The Amazon was one of the least explored places in modern history, but beneath its towering trees and twisting vines lies the memory of a hidden cityscape, a web of buildings, gardens, roads and canals, centuries old, swallowed by the wilderness itself and for a while lost completely. But what was once forgotten is now being rediscovered. Satellite imagery and laser scanning techniques have combined to bring a new version of the Amazon to life. A rainforest that's been shaped by humans for thousands of years, not only through spectacular buildings, but by manipulating entire ecosystems, networks of creatures that were only just beginning to untangle. Those creatures make up 10% of the world's wildlife species and a new plant or animal species is discovered every other day in this great forest. But these are the only treasures hidden in the Amazon. Whatever came of the lost city of El Dorado. I'm James Shewitt and you're watching Astrum Earth. Join me in this video as we venture beneath the canopy to find a different story of the Amazon. From the early explorers that left clues centuries ago to the modern science finally deciphering the code, to uncover the true secrets hidden in the rainforest. And we'll be answering one big question. What still might be waiting to be found? With 6 million square kilometers of continuous green canopy, the Amazon comprises more than half of Earth's total remaining rainforest. For centuries European explorers spread rumors amongst themselves that there was a legendary wealthy city deep in the Amazon. They called it El Dorado, the city of gold. In 1542, Spanish conquistador Francisco de Oriana reported traveling down the Amazon and finding vast rich lands with farms, villages and even large walled settlements. But when others later followed his route, they found only impenetrable jungle and small groups of hunter-gatherer tribes. Scientists assumed that Oriana's story was just that, a story. Nothing but the fanciful dreamings of a gold-hungry conquistador. But the search for El Dorado did not stop there and actually lasted for more than a century. Established explorers like Gonzalo Pizarro, Philip von Harten and even Sir Walter Riley all led separate expeditions from 1541 to 1617. The result? Well, nothing but disaster, death and the further conquest of the indigenous people. But the allure of finding the unfindable endured well into the 20th century too. When British explorer Percy Forset became obsessed with finding the riches Oriana had described centuries earlier. Fueled by the fire of one main objective, to find what remained of a lost city he called Zed. He focused on the western Amazon in Bolivia and the southern Amazon in Brazil, but found nothing. Along the way he did encounter indigenous people, but found them living in small villages. A far cry from the huge cities the rumours had promised. Rather than deter him, this seemed to spur him on even more. He even wrote to his wife in a letter that she need have no fear of failure. Yet on the 29th of May 1925 on his eighth Amazonian expedition, Forset headed into the jungle from a place somewhere in the Mato Grosso region of Brazil known as Dead Horse Camp. Never to be seen again. For decades after this last hurrah really, scientists concluded that this place was simply too hostile, too inhospitable for humans to thrive. And was largely just an expanse filled with exotic flora and fauna. Feedback among the scientific community was that the rainforest soil was so poor, it simply could not sustain large-scale farming and therefore cities were impossible. But they were all missing something, something that actually forced it have been onto. Because it turns out he was looking roughly in the right places, but maybe he was looking for the wrong things. Now up until this point the rainforest had done a pretty phenomenal job of camouflaging its secrets. But just five years ago everything changed. Scientists finally found the lost cities of the Amazon because this time they had something these explorers didn't. They had lasers. Yeah, I know not what I was expecting to say either, but this is this is pretty amazing. In the end the tool that cracked open this mystery is LIDAR. Light detection and ranging. Oh, yeah, essentially lasers. LIDAR works by sending pulses of laser light out towards objects and measuring the time it takes for the reflected laser beams to return. And with a bit of maths as speed is distance over time and we know the speed of light, we can then work out the exact distance to those objects. Over vast areas taking lots of measurements. That means we can generate precise 3D information about Earth's surface. And in rainforest archaeology that becomes something almost magical. You can scan the canopy and then remove it digitally and then see the ground like the forest isn't even there. And what it revealed was astounding. Now I should quickly say LIDAR doesn't show us ancient civilizations on its own. But it does show us shapes, micro topography, geometry, the fingerprints of organized Earth moving. Then the archaeologists go in and do their bit. They excavate, they date stuff, they test the story the terrain is telling. But as a first step, LIDAR is like looking into your attic with X-ray vision and finding that family heirloom you thought you'd lost without opening a single box. And in the Amazon it did not disappoint. In 2022, using this new airborne technology, archaeologists Heiko Prumas and his colleagues mapped settlements associated with the Kaserabe culture, which thrived around AD 500 to 1400 in the Yanos-Demohos region of Bolivia. But this wasn't just a splattering of small villages, it was an entire system. They had found a hierarchy, a landscape engineered for humans. Two main sites stood out from the LIDAR imaging data, enormous in area. 147 hectares and 315 hectares respectively, the size of nearly 400 soccer fields. The sites were embedded in a four-tier settlement system with incredibly advanced architecture, including platform mounds and conical pyramid-like structures. Straight causeways ran for kilometres and canals and reservoirs formed a water management network across the landscape. What this was was a tropical form of urbanism, a way of living and a city built from the rainforest itself. And if one hidden city had finally been uncovered then the question was unavoidable. What else was hiding? The answer lay in Ecuador. In early 2024, a science study using the same LIDAR techniques revealed a dense settlement network in the Upano Valley of Ecuador along the eastern foothills of the Andes Mountains. The work led by archaeologists Stephen Rostain and his colleagues integrated decades of field research with LIDAR mapping and with this combined knowledge they uncovered the unthinkable. Within a 300 square kilometres survey area they found more than 6,000 anthropogenic rectangular earthen platforms and plaza structures connected by footpaths and roads, some 13 metres wide and surrounded by expansive agricultural landscapes and even drainage features. In other words, what they were looking at was not just a single lost city, this was a patterned regional network. They were looking at a hidden metropolis. The sheer scale of this discovery meant it was likely home to at least 10,000, possibly 30,000 inhabitants in around 500 BCE with the settlement lasting roughly a thousand years. And if you're wondering by the way how on earth we know that this was happening that far back, well science has another trick up its sleeve to answer that question too. 2. Enter Oxford's Radiocarbon Accelerator Unit This team applied radiocarbon dating to organic materials to find out just how old this civilisation was. To quickly explain how this works, every living thing absorbs carbon from the atmosphere, whether that's through photosynthesis or eating stuff that photosynthesises. Now most of that is your regular carbon 12 which has 6 protons and 6 neutrons, but a tiny percentage about one in a trillion particles of carbon is carbon 14, which still has 6 protons but has 8 neutrons so it's slightly heavier. Now living things aren't very picky about this and will take in either type of carbon really, but crucially carbon 14 is radioactive and so breaks down naturally over time. And what this means is the moment a plant or animal dies the clock starts effectively, it stops taking in carbon 14 and as it decays the amount of carbon 14 in the organism decreases. It's half life therefore that's the time taken for half of the carbon 14 in a sample to decay is around 5700 years. As such scientists can measure what percentage of the carbon in a sample is still carbon 14 and from that can calculate how many years have passed since that organism died which is really clever. When used in tandem these two techniques reveal incredible things. Think of Lidar as finding the where and the radiocarbon dating determining the when. As amazing as all these discoveries undoubtedly are they are just zoomed in examples of the mysteries the canopies hid and their hints of something far larger. Really Bolivia and Ecuador were just the close-ups the next step is the wide shot and here here's where things get wild. In 2023 Brazilian geographer and remote sensing specialist Vinicius Peripato did something pretty bonkers. He applied this same concept but on a far larger scale taking an amazon wide approach to hidden archaeology. He and his team used Lidar data originally collected for forest biomass work and scanned 5,315 square kilometers across the basin which yes might sound impressive but remember this is the amazon that's roughly 0.08 percent of the whole thing. But here's where it gets interesting because even in that tiny slice of this monstrous green pie they identified 24 previously undetected earthworks beneath the closed canopy. Now if you were to apply those same numbers to the unscan parts of the rainforest they estimated there are between 10,272 and 23,648 large-scale earthworks still waiting to be discovered with many likely concentrated in southwestern amazonia. What? Peripato's team also found statistical links between earthwork probability and dozens of domesticated tree species 53 to be precise. Now what this means in real terms is that ancient people shaped the forest. The species that increased near earthworks were very likely planted protected and even encouraged. This part of the amazon shows huge long-term human influence. If if these predictions hold true it just goes to show that hidden doesn't necessarily mean mythical. It means not yet measured at the right resolution in the right dimension and by the right method. And speaking of there is still one place that so far alluded all of these scientists. El Dorado. Do you know what I wish would elude me? Data brokers. Those annoying people that are more than happy to sell my personal info to the highest bidder. Things like my email address, home address and family information. Trust me this is one instance I'd love to stay hidden like one of these amazonian cities. No matter where I go they always seem to find me. Maybe they're using LiDAR too come to think of it. Anyway luckily this year I've been using delete me. It removes my personal information from those websites and honestly it's been a total game changer. When I first started using it at the start of the year I had six data breaches which put my data at significant risk. But luckily thanks to delete me I now have zero. Last week I had a couple of spam emails that came in and that have my personal information and all I had to do was simply make requests via the online portal for them to look into and it was sorted out really quickly. And it's very satisfying to shut down those spammers I must admit. So if you'd like to disappear beneath your own digital canopy why not join delete me? I promise there are no lasers involved and they're giving our viewers an awesome deal. 20% off with my link join delete me dot com slash astrum earth and use code astrum earth at checkout. Thanks to delete me for sponsoring this video the link is in the description if you want your digital life a bit more private as we head back to Eldorado. Yeah we touched on this place right at the start of the video and it turns out the reason we cannot see it is because it never existed. Yeah sadly if all of those would-be treasure hunters the gold one was actually not a place but a person. The name comes from the Moisica people who lived high in the Andes of modern day Colombia from AD 500 and still due to this day actually. To the Moisica gold wasn't a symbol of wealth or private treasure it had a deeper meaning it was it was sacred. During rite of passage ceremonies a new ruler known by the Spanish as Eldorado or the golden one would undergo a dramatic ritual. His body would be covered head to toe in gold dust and he would set out on a raft into the center of a sacred lake most famously Lake Guatavita 75 kilometers northeast of what is now the capital Bogotá. Once in the center priests and attendants would cast gold and precious other things into the lake as offerings then covered in gold the ruler might submerge himself into the water and return to shore with the remaining dust washed off his skin and remaining in the water. When Spanish chroniclers like Juan Rodriguez Freylae in the 16th century shared the second hand stories over many centuries stories of immense gold offerings and dazzling ceremonies became more than just decorated leaders they turned into a whole city full of treasure that Europeans just sort of reimagined. Soon the idea had taken on a life of its own and just as cartographers redrew maps to include lost cities like Atlantis the name Eldorado also started to appear. Fortunately though science eventually intervened and remarkably a gold raft depicting the exact same we've just described was found in 1969 by three villages. It was hidden away in a small cave in the hills showing the man covered in gold going out into a sacred lake the real story of Eldorado. So yeah in the end scientists weren't able to uncover a city of gold but they did find something arguably way more valuable. Now we go deeper literally because one of the Amazon's strangest secrets isn't in a wall or a road but instead is it soil. Bear with me here I know that doesn't sound as exciting but trust me it is because if humans lived in all those amazing sites we've showcased in this video which does seem very likely how did they exist in spite of the rainforest naturally poor and nutrient depleted soil how did they grow stuff it's impossible right. Remember at the start of the video when we said all of those expeditions right from the 1500s to poor old Percy Fawcett in 1925 all of those had scientists saying part of the reason the cities couldn't be found was because the soil was too infertile to support human life remember that well modern day science has since shown that to be wrong too actually but in the most shockingly brilliant way. New research shows something surprising ancient Amazonians intentionally created patches of rich dark soil known as terra preta or Amazonian dark earth to make farming possible and this was no accident in fact they're still doing it today modern indigenous communities like the kwee kuru still make dark fertile soil by firstly piling up food scraps and organic waste then spreading charcoal and ash around fields before finally creating these compost middens. Over time these practices produce carbon rich soil that thrives with nutrients even in a region where untouched soils are typically infertile. Try and get your head around this ancient Amazonians weren't just passive forest dwellers they actively managed landscapes they created fertile ground to grow crops and support large populations and there's another bonus too because dark earth holds huge amounts of carbon these practices incidentally locked carbon into the ground for centuries or even millennia that makes terra preta not just fertile soil but a potentially powerful example of long term carbon sequestration and that soil does way more than just help provide food woven into all of this is the fact that in almost every example we've talked about in this video the forest itself is part of the construction. In an article published in Science in 2017 Levis and colleagues compared distributions of domesticated woody species with archaeological sites and environmental data and the link they established between them was mind-blowing. They reported that domesticated tree species are far more likely to be hyper dominant where a small subset of species makes up a disproportionately large percentage of the total individuals or biomass in an ecosystem and that the richness and abundance of domesticated species increases near archaeological sites. Now this doesn't mean every single hectare of the Amazon forest was designed but it does mean the old binary of pristine versus human is too simple. The Amazon can be wild and historical at the same time and in a cruel twist of irony all of that carbon that the soil locks in is the very thing that's most under threat. The Amazon holds roughly 150 to 200 billion metric tons of carbon in its forest and in its soils an amount comparable to the last four to five years worth of global CO2 emissions. In tact Amazon forests work as carbon sinks helping reduce the impact of emissions on our atmosphere but that sink has weakened and in 2019 parts of the Amazon actually released more carbon than they absorbed. This means that if the Amazon continues to shrink or indeed was lost entirely the impact would be catastrophic essentially releasing in the order of hundreds of billions of tons of carbon into the atmosphere and dramatically altering regional and international climates. Recent data shows Amazon deforestation soared to more than 10,000 kilometers squared per year between 2019 and 2021 before in force efforts to drive it down again in 2023 to 2025. Severe wildfires in drought years have also released large amounts of carbon. For example satellite-based measurements found Amazonia emitted between 28 and 62 billion kilograms of carbon monoxide in 2024 from wildfires alone approximately four times the average. These trends underline that the Amazon's carbon bank account is being depleted increasing risks of future climate impacts if not urgently addressed which raises one big question doesn't it? What does the future look like? So far we've only really covered the ancient hidden human elements in this gargantuan rainforest but what about what else might live there? The Amazon's biodiversity is so rich it feels almost endless. One in ten known species on earth lives here but how many more species are out there that no one's catalogued yet? I wish I could give you a nice round number to go off and continue your day with but the answer is actually way more exciting well at least to me anyway. Even the best estimate suggests that only 20% of earth species have been documented by western science with potentially millions more unknown and unnamed. Even in the last few years new species are being uncovered every single day. The Royal Botanic Gardens in Q reported that 172 new plant and fungus species were described globally in 2024 alone many of them in tropical regions. The same applies to animals too. A WWF survey found 441 new species within the Amazon rainforest over the span of just four years that's roughly one new species every three days it's staggering. In 2024 alone scientists found a blob-headed catfish a new marsupial in Peru three new amphibians and even a new species of anaconda the northern green anaconda casually the largest and heaviest snake in the world all in parts of the Amazon rainforest and not for the first time science is supercharging this process because we now have ways to sample the jungle without ever having to see the animal. A cutting-edge advancement in environmental DNA called EDNA means all we have to do is simply filter water when looking for genetic animal traces. A landmark 2016 study found that rivers act like conveyor belts of biodiversity information. In real terms water samples essentially contain trace amounts of DNA from fish, frogs, even land mammals from upstream so scientists can vacuum river water through a filter and then do DNA sequencing or PCR. This is called environmental DNA or EDNA it's like fishing for genes you pull up the filter and see whose DNA is there and in 2026 they put this theory to the test. Caitlyn Ramosa an aquatic ecology and conservation scientist at Texas A&M University and her colleagues developed a portable EDNA protocol to map Amazonian manatees. Now these creatures were known to inhabit the region but were very hard to observe directly due to the murky water and their elusive behavior making them perfect for this study. So what she and her team did was filter water along the Amazon for 13 days taking samples without even using a freezer by the way these a special preservative and amazingly they still recovered manatee DNA. They found manatee genetic material at multiple sites in the central Amazon. What this means in short is you can essentially sit there on a river bank collect a couple of water samples and later find out what elusive animals live upstream it's a game changer. As we reflect on all the amazing things we've just talked about the word of caution as we come to the end of the story here as the picture of what's hiding becomes more and more clear we must still protect what is vulnerable. The Amazon includes territories of indigenous peoples in voluntary isolation some of which have never come into contact with the outside world. As such you might have noticed when we reference the LIDAR articles we do not name precise coordinates of sensitive sites. We must treat indigenous communities as living homelands not just adventure backdrops for us to sit here and make videos about. So to wrap things up what's hiding in the Amazon the question I posed at the start not a single lost metropolis not a single myth but a layered reality evidence of ancient cities that only lasers can see soils that store human history for hundreds of years forests shaped by past cultivation and species that remain invisible until we sample a river. To be honest part of the reason I wanted to make this video was to challenge misconceptions I've seen all over social media that 60% of the Amazon remains unexplored and loads of stuff as to why that might be but ultimately and hopefully as we've shown these landscapes weren't lost to everybody local communities and indigenous oral histories often remembered them in the stories of their ancestors or practices handed down over generations. Our modern scientific methods are just a flashlight really to shine a light on the whole picture we must look at all the evidence around us and then well we might find something truly incredible like the city of Alderado or not. Let me know in the comments below what you think or even hope might still be waiting to be discovered in the Amazon or maybe you don't like the idea of finding stuff and sometimes the unknown the hidden remains the most exciting thing.
