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
[music] 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 [music] 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 aren't the only treasures
hidden in the [music] Amazon. Whatever
came of the lost city of El Dorado?
I'm James Sherritt and you're watching
Astrium 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. [music]
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
Orellana 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 Orellana'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
it lasted for more than a century.
Established explorers like Gonzalo
Pizarro, Philip von Hutten, and even Sir
Walter Raleigh all led separate
expeditions from 1541 to 1617.
The results? Well, nothing but disaster,
death, and the further conquest of the
indigenous people. [music]
But the allure of finding the unfindable
endured well into the 20th century, too,
when British explorer Percy Fawcett
became obsessed with finding the riches
Orellana had described centuries
earlier, fueled by the fire of one main
objective, to find what remained of a
lost city he called Z.
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
rumors 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, Fawcett
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 Fawcett had 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 5
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 uh 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 Prumers and his colleagues mapped
settlements associated with the Casarabe
culture which thrived around AD 500 to
1400 in the Llanos de Mojos 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 [music]
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 kilometers
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
archaeologist 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
kilometer survey area, they found more
than 6,000 anthropogenic rectangular
earthen platforms and plaza structures
connected by footpaths and roads some 13
m 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 [music] in
around 500 BCE with a settlement lasting
roughly a thousand [music] 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.
Enter Oxford's radiocarbon accelerator
unit. This team applied radiocarbon
dating to organic material to find out
just how old this civilization was.
To quickly explain how this works, every
living thing absorbs carbon from the
atmosphere, whether that's through
photosynthesis or eating stuff that
photosynthesizes.
Now, most of that is your regular
carbon-12, which has six protons and six
neutrons. But a tiny percentage, about
one in a trillion particles of carbon,
is carbon-14, which still has six
protons but [music] has eight 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.
Its half-life therefore, that's the time
taken for half of the carbon-14 in a
sample to decay, is around 5,700 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
pretty 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 they're 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 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%
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
unscanned 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
methods. [music] And speaking of, there
is still one place that's so far eluded
all of these scientists.
Eldorado.
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 for all of those would-be
treasure hunters, the gold one was
actually not a place
but a person.
The name comes from the Muisca people
who lived high in the Andes of
modern-day Colombia from AD 500 and
still do to this day, actually. To the
Muisca, 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 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 km 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 Freyle in the 16th century
shared these 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 El Dorado also
started to appear.
Fortunately, though, science eventually
intervened. And remarkably, a gold raft
depicting the exact scene we've just
described was found in 1969 by three
villagers. 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 El Dorado.
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 its
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's 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 [music]
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
Kuikuro still make dark, fertile soil by
firstly piling up food scraps and
organic waste, then spreading [music]
charcoal and ash around fields before
finally creating these compost middens.
Over time, these practices produce
carbon-rich soil that thrives with
nutrients, [music] 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 4 to 5 years'
worth of global CO2 emissions.
Intact 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 km² per year
between 2019 and 2021 before enforced
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 [music]
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 10 known
species on Earth lives here, but how
many more species are out there that no
one's cataloged 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 estimates suggest that
only 20% of Earth's 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 Kew
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 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.
Caitlin 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 are 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 could
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 remember
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 El Dorado.
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.