Original subtitles

(dramatic music)

- [Narrator] The world's greatest structures

push the boundaries of engineering.

All fueled by a constant desire to innovate.

- Without engineering, there would be no modern world.

- [Narrator] Gigantic buildings,

complex infrastructure and ingenious inventions.

- Engineering is the key that turns dreams into reality.

- [Narrator] Many of today's incredible achievements

rely on breakthrough technologies

first devised by ancient engineers.

- It's astounding how they achieve this.

- [Narrator] Early civilizations

built on an unimaginable scale

and with incredible precision.

- They raised a bar for engineering

in a way that no one thought possible.

- These are some of the finest engineers in history.

- [Narrator] Redefining the known laws of physics

and dreaming up the impossible.

They constructed engineering wonders,

from colossal stadiums to mighty waterways

and complex machines.

All with the simplest of tools.

- You cannot imagine the skills

people would've needed to build like this.

- [Narrator] By unearthing the mysteries

left by these ancient engineers,

we can now decode their secrets.

- That so many of their creations still survive

is testament to their engineering prowess.

- [Narrator] And ultimately reveal how their genius

laid the foundations for everything we build today.

(gentle music)

It's the most luxurious element on the planet.

A metal like no other.

The ultimate symbol of wealth

and success.

(crowd cheering)

Gold.

It obsesses us and has captivated cultures

around the world throughout history,

inspiring legends of lost cities

and kings with the Midas touch.

- It's beautiful.

It's burnished.

There's a warmth to gold.

Something that draws human beings towards it.

Almost like it sort of warms human nature.

- Gold's the most wonderful material.

It's malleable, it doesn't decay.

So it's very useful, as well as very attractive.

- [Narrator] And what makes gold

especially valuable is it's rarity.

- It's that sort of Goldilocks thing

of being rare enough to tempt people to want it,

but not so rare that nobody can have it.

- [Narrator] In fact, it's estimated that

all the gold extracted from the earth so far

would fit into a 65 foot cube.

Only a few times bigger than a semi-detached house.

Since ancient times, the pursuit of gold

has driven engineers to devise new techniques

to mine,

process

and refine it.

- The desire for gold actually led to huge

technological and engineering advancements.

- [Narrator] Their inventions have shaped modern society.

- They've established the global markets we have today.

It changed the world forever.

- [Narrator] And these ancient breakthroughs

are still prompting us to cross frontiers,

building the deepest mines,

creating the latest technology...

- [Announcer] Three, two...

- [Narrator] Even venturing-

- [Announcer] Zero.

- [Narrator] Into space.

But how did these ancient engineers

first discover gold's unique properties?

There's no clear evidence

for when gold was first discovered.

The earliest surviving objects in the world

date from over 6,000 years ago

from sites in the Black Sea and the near east.

But earlier humans may have found gold long before this.

It simply washed up at their feet.

- If it's in a riverbed, you'll see the gold glinting.

It doesn't rust,

it doesn't dissolve in water or do anything.

So it's there and it's lying there.

It's getting rounded and bumped around a bit,

but it's in the river bed.

- [Narrator] It's likely that this river, or alluvial, gold

would've caught the eye of ancient peoples,

who began to experiment with it.

- One could imagine that the very first discovery,

when someone picked it up and said,

"Hey, look, I can hammer this into a nice object."

Would have been an alluvial nugget, it's obvious.

- [Narrator] But how did it get there?

Gold can only be created by extreme energy

produced inside rare supernova

or the collision of neutron stars.

All of the gold on Earth, therefore,

likely comes from outer space.

Much of it from meteorites and boulders,

which slammed into its surface billions of years ago.

Most of this gold is buried deep,

but some has been brought closer to the Earth's surface

around tectonic plates through volcanic activity.

Super heated water transports dissolved elements,

including gold, up through the crust

where they solidify into hard veins.

Over time, as water erodes these veins,

tiny pieces wash into rivers.

And as gold is one of the least reactive metals,

it will not corrode and can stay here indefinitely.

- When it comes out the ground

it's as shiny as the day it went in, you know,

and I think there is an element of that

that's captured the imagination

of past societies going way back.

- [Narrator] Early gold gathering

may simply have been done by hand.

But to find gold hidden deeper among the river deposits

required a more specialized solution.

- And the natural progression is to try a basin,

whether it was of wood, pottery, early bronze or whatever.

You swirl it round and, if you're lucky,

there'll be few little bits of gold glinting

in the bottom of the bowl at the end of it.

And that's gold panning.

- [Narrator] Gold panning was likely

ancient man's main extraction method.

And alluvial gold is estimated to have provided

two thirds of what was ever produced.

Because the panning process is so simple,

it has remained a widely used method to this day.

(gentle music)

Facilitating some of the greatest gold rushes of all time.

- [Male] There was gold for all.

Gold seekers were stirred to a frenzy

by tales of glory holes and rich diggings.

- [Narrator] In 1848, gold was found in California,

sparking the famous American Gold Rush.

In just over a year, California's population

increased from 14,000

(upbeat music)

to almost 100,000.

- Once the news gets out, all hell breaks loose

'cause people want to get it and go for it.

It's this optimism and greed going for it.

- [Narrator] In their haste to find gold,

these prospectors even abandon their ships

in the Bay of San Francisco.

The remnants still lie buried under the financial district.

To look for gold, they headed to the mountains and,

initially at least, just use

simple panning methods to find it.

- Panning for gold is an incredibly democratic method.

You don't need many resources,

you don't need much training or skill.

- [Narrator] But this technique is labor intensive,

time consuming, and it doesn't get you much gold.

To find more, the ancients needed

to follow the trail underground.

(dramatic music)

To reach the motherload.

Few ancient cultures are more associated with gold

than the Egyptians.

Famed for their elaborate engineering projects,

gold was central to Egyptian culture.

Used for opulent decoration, jewelry and statues.

In fact, the hieroglyph for gold

first appeared with the beginning of Egyptian writing

in the very first dynasty.

The Egyptians believed that gold

was the flesh of the sun god Ra.

So were not far off about its stellar origins.

- For the Egyptians, gold was associated with divinity.

It was associated with creation.

It was literally the most significant, powerful object

you could imagine.

- [Narrator] The ultimate luxury material,

gold was coveted in life.

But it was just as important in death.

- Whether you're a pharaoh or quite an average person,

you wanted to have goods to take into the afterworld.

You'd need things.

Because gold doesn't decay,

it was the perfect material to cover a body with

'cause it would last for maternity,

which is what they hoped the body would.

- [Narrator] Egypt's geology meant that

it naturally had large quantities of gold.

But the amounts the Egyptians desired

couldn't be found in a river alone.

So they opted for a different solution,

(dramatic music)

mining.

While they weren't the first to mine gold,

the Egyptians certainly took it to a new industrial level.

And without modern prospecting methods, like remote sensing,

locating this so-called gold of the mountain

was all down to a simple realization.

- Finding gold for the Egyptians

rested on the observation that gold

was often associated with quartz.

So if you followed the quartz,

you were more than likely to find the gold.

- [Narrator] To access it, these ancient engineers

developed tools to help them smash open the rock.

If a vein went deeper, they would follow it,

digging tunnels and shafts.

- This would've been laborious,

backbreaking and terrifying work.

- [Narrator] And the scale of Egyptian

gold production was unprecedented.

- One of the most remarkable survivals

connected with gold from the ancient world

is not a gold object, but it's a map

that actually shows the gold mines.

- [Narrator] One of the oldest surviving maps in the world,

the Turin Papyrus.

(gentle music)

It predates equivalent modern geological maps

by almost 3000 years and is one of the first maps

to represent real geographical content.

But it's what it reveals about

the organization of Egyptian gold mining

which makes it particularly incredible.

Created during the reign of Rameses IV in around 1150 BC,

it records many places in the Eastern Desert

where the Egyptian state was mining and processing gold.

- Rather than it was a case of sort of,

this is how you get to the mines,

I think it was some sort of bureaucratic use for the map

to keep a record of the mines and maybe their output

or how many slaves you had working.

- [Narrator] And when archeologists in the 1980s

started to map ancient Egypt's gold mines,

what they found was staggering.

Up to 250 of them scattered across the Eastern Desert.

(dramatic music)

While today mechanical diggers

bear the brunt of mining work,

in ancient times, this process was labor intensive,

requiring thousands of paid workers,

or sometimes slaves to mine and process the gold laden rock.

Over time, they developed millstones

to crush small pieces of quartz ore to a fine powder.

And, once ground, the Egyptians devised various ways

to separate the gold from the rock.

One of these was a technique known as winnowing.

The finely ground gold ore was shaken inside a dry blanket

to create pulses of air,

which separated the rock from the gold.

This movement also created a static charge,

which stuck the gold to the fabric.

So when the blanket was opened,

the rock dust would blow away, leaving just the gold.

- This is something they'd used anyway with crops.

What you would use is either a blanket or a basket

and you'd throw them up and you'd just throw it up.

And the wind would carry away the chaff

and you'd be left with the wheat.

And it's the same principle that they're using

to separate out really, really small particles of gold

from small particles of dust.

- [Narrator] But winnowing wasn't the only way.

Where water was accessible, the Egyptians engineered

another even more effective method, washing tables.

The ground powder and water would be

poured down a slanting table.

Materials like sheep's wool spread over it

would catch the heavier gold particles,

while lighter rock would be washed away.

And, to ensure no gold was missed,

over time, sophisticated circulation systems were developed

to feed the runoff back to the start.

- Wool has sort of residual oils and lanolin in it.

So, as you are washing in the wool,

what's happening in that process is that the heavier gold

is being trapped within the wool.

Now, once you've achieved that,

it's a very simple step to drying it out

and then burning off the wool to leave the gold residues.

- [Narrator] Also used to catch gold in streams,

it's possible that the use of sheep's wool

may even have inspired the famous Greek myth

of Jason and the Golden Fleece.

(dramatic music)

Today, electric powered machines now do

what thousands of Egyptian workers once did,

crushing the rock and washing it on shaker tables

capable of processing up to two tons

of gold laden rock per hour.

The Egyptians' thirst for gold was so great,

from as early as 2000 BC, they even sought to control

their neighbors to the south, in modern day Sudan.

Known in ancient times as Nubia,

it was the gold center of the ancient world.

It's opulent objects reflecting its wealth of natural gold.

Wall paintings record how wars were fought

to control these gold rich territories

and how Nubians were made to bring

tributes of gold to the pharaoh.

- And we have one vulnerable thing with the pharaoh saying

basically, he commanded the chiefs of Nubia to mine gold.

I think he just couldn't get enough of it.

- [Narrator] Almost 3000 years ago, during the 12th dynasty,

the Egyptians even built a system

of highly fortified mud brick strongholds on the Nile

to police this trade and ensure a constant supply.

- It was a huge enterprise,

from both ensuring you had the access to the mines,

ensuring that the locals were playing ball with it

and then the bureaucracy to cope with it and deal with it.

- [Narrator] But to turn raw gold into objects,

ancient engineers needed to melt it

into more workable forms.

And there was a problem.

- So, to melt gold, you need to be able to create

these really high temperatures, right?

Now, if you're burning with just a standard wood fire,

you wouldn't get that temperature.

- [Narrator] An ordinary wood fire burns

at only around 1100 degrees Fahrenheit.

Whereas gold's melting point

is several hundred degrees higher.

So, to increase the heat,

the ancient engineers turn to even older methods

devised for producing another metal entirely.

(dramatic music)

From at least as early as the sixth millennium BC,

in societies across the eastern Mediterranean and near east,

techniques had been developed for pottery production

and to melt other metals, such as copper.

For these purposes, ancient smith's created furnaces and,

instead of wood, they powered them using charcoal.

- Charcoal is a very, very good fuel.

Awful lot of heat in it

and it's very pure too so it doesn't contaminate.

- [Narrator] As this technology spread,

soon charcoal was used to melt gold too.

Egyptian reliefs reveal how the process was refined

using blowpipes to increase the heat even further.

The first pipes were likely just hollow reeds,

but, as these burned easily,

fire resistant clay tubes began to be used instead.

However, they were still not particularly efficient

and often required several people all blowing at once.

- The problem with using your own lungs

is that actually you are already extracting

some of the oxygen from the air that you're blowing out

and what the fire needs is oxygen.

So just sitting there with blowpipes

trying to get the heat up,

actually isn't the most effective way

within which you want to actually roast down that gold.

- [Narrator] So, for large scale gold production,

the ancients hit upon a better idea, the pot bellow.

To make the bellow, animal hide was stretched

over a wide clay pot.

When the surface of the hide was pushed down,

it forced air out into the furnace.

To replenish the supply, the hide was lifted

and air flowed in through a valve.

Pot bellows could be operated by alternate feet,

meaning that only a single operator was needed

to produce a continuous air supply.

- It's a very effective way of doing it.

I mean the later versions like the bellows

you used to see beside every fireplace

with the sort of two bits of wood you pumped,

I mean, that's just a later version of it.

So it is not complicated, but it's very effective.

I mean, I feel like it's engineering

with very simple materials.

- [Narrator] Bellows were major development.

Whereas blowpipes could supply around

4.5 gallons of air per minute,

pot bellows could deliver around 10 times that.

- The more air you can get into the fire,

the hotter the flame.

- [Narrator] This greater efficiency meant that

more and more gold could be extracted

on an industrial scale.

Furnaces and bellows have evolved through history but,

without these early inventions,

it's fair to say the developments which shaped

modern industry may never have happened.

- These early breakthroughs directly led

to the invention of the coke-fueled blast furnace,

which allowed you to smelt iron and turn it into steel,

powering the industrial revolution.

- In a sense, you could look at

the sort of a modern motorcar factory

and sort of draw a line right back

to the first guy with a furnace for pottery

in wherever it was.

- [Narrator] Now the ancient engineers could melt gold.

This opened up brand new design possibilities.

(gentle music)

Melted gold could be made

or cast into different solid shapes

through a technique known as the lost wax method.

This involved first making a model out of wax

and then entirely covering it in clay,

except for a single hole.

When the object was baked, the clay hardened

and the wax drained away.

Molten metal could then be poured into it,

creating an exact replica of the original.

Once the ancient engineers could cast gold,

they could let their imaginations run wild.

Gold could now be made into jewelry,

created into objects to adorn palaces and temples,

and even placed in tombs.

But, incredibly, the earliest known example of cast gold

is from a tomb which predates even the pharaohs.

Recent analysis of finds discovered in Bulgaria in the 1970s

could rewrite the history books.

Varna on the Black Sea is home to the oldest surviving

funerary hoard of gold objects on the planet.

Dating to around 4,550 BC, these were created

by a mysterious society only a few centuries

after the first farmers came to Europe from the east.

And it's unprecedented in scale,

with over 3000 gold artifacts.

- Little is actually known about this society,

but the majority of the objects were discovered

in just five graves and that suggests

that they had an elaborate social hierarchy.

- [Narrator] Although Varna's gold objects

were long thought to have been hammered

from raw gold nuggets, recent analysis suggests

that some were in fact cast from melted gold,

making it potentially the earliest known example

of this technique anywhere on the planet.

Many ancient cultures,

particularly in south and central America,

where gold was abundant,

also produced gold objects this way,

giving rise to legends of entire golden cities,

which enticed European explorers.

It's a method still widely used in the modern world

with applications in many industries,

not least gold crowns in dentistry.

And it's one of the most common ways

of mass producing jewelry.

Though now there's a twist,

instead of laboriously carving wax by hand,

3D printers are now often used to sculpt

the master mold in resin,

a modern update on an ancient method.

- Today you go down the high street,

the vast majority of jewelry is produced by casting

'cause it's quick, it's easy, it's efficient

and you can do it on a huge scale.

- [Narrator] But to cast larger

solid objects out of gold is expensive.

So, to make this precious material go further,

the ancient engineers turn to another

of gold's unique properties, it's malleability.

- Pure gold is infinitely malleable.

In other words, you can carry on hammering,

bending, hammering, and it never breaks.

- You can squash it, you can take your little ingot of gold,

you can wallop it with a hammer

and it'll spread out into thin sheet.

(gentle music)

- [Narrator] Ancient Egyptian wall paintings

illustrate how workers beat the gold

with a round stone to make it flat.

And such gold had a number of uses.

Famously, in one of the 20th century's

most incredible archeological discoveries.

Uncovered in 1922 by Howard Carter,

the tomb of boy pharaoh Tutankhamun

was one of the most lavish of all time,

containing over 5,000 objects, many of them gold.

But his funerary mask is its glorious centerpiece,

only made possible because of gold's malleability.

- Of course, one of the great benefits of using sheet gold

to create something is that it can be hollow.

So when I think of it, I mean,

Tutankhamun's mask is obviously thin gold.

It's not solid head.

So you've got this hollow inside.

So it looks more than it is.

- [Narrator] Created from two sheets

softly hammered into shape, the mask perfectly enclosed

the pharaoh's head and shoulders,

giving him the golden skin of a god for eternity.

- Only with gold could they create such unparalleled detail.

The finest of facial features.

- [Narrator] But such extravagant use of gold

was not practical for anything less

than a pharaoh's funeral.

So, to make it go even further,

the ancient engineers came up with a plan.

They simply kept hammering it.

- It's a very simple mathematical progression.

The thinner you hammer the gold,

a bigger area you can cover with it.

There must have been a push to get the gold

thinner and thinner and thinner.

- [Narrator] The ancient engineers discover

that hammering sheet gold for long enough,

produced a gold foil, roughly as thin as a newspaper page,

which they could then pin

or stick to an object using an adhesive.

- You can pick it up and wrap it round

whatever it is you are trying to gild, so to speak.

- [Narrator] But gold's malleability

could take it even further.

If this foil was beaten between sheets of animal hide,

to stop it cracking, it could be made so thin

it could create a brand new material,

gold leaf.

(gentle music)

Gold this thin could be used to gild much larger surfaces,

making objects appear as if made of solid gold.

- Because it is so soft, it is able to go into

every little interstice and this makes it self adhering.

The two surfaces so intimately bonded together,

they are becoming cohesive.

- [Narrator] The Roman author, Pliny the Elder wrote

that a single ounce of pure gold

could be beaten out into 750 leaves or more.

That's the equivalent of under one micron in thickness,

over 70 times thinner than a human hair.

Today, with modern methods, gold can be made even thinner

for yet more diverse purposes, such as makeup,

or even to decorate food.

- Goodness knows why people would eat gold leaf

other than for issues of prestige,

but it's an inert substance.

It's relatively safe to eat,

provided it's in small enough particles

and it will pass out the other end, I guess.

- [Narrator] In several Eastern religions,

including Buddhism, gold is believed

to symbolize knowledge or purity

and gold leaf is still produced the traditional way

to cover many sacred objects,

from statues to giant holy rocks.

It can even be used to coat entire buildings

and make them appear as though made of solid gold.

(dramatic music)

The Shwedagon Pagoda.

This Buddhist stupa, or sacred ornament,

is believed to contain the relics of Buddha himself.

And at over 300 feet high,

it towers above the city of Yangon in Myanmar.

Whereas gold in other ancient cultures

was often found inside temples,

this building is thought to be solid and cannot be entered.

It's gold is likely all displayed on the outside.

- The Shwedagon Pagoda in Myanmar

is one of the most revered shrines in Buddhism.

There's a legend that golden nuggets

rained down from the sky

and they were used to build the pagoda.

But, in reality, only its surface is made of gold.

It is almost entirely covered in gold leaf.

And as this material can't be produced in very large sheets,

creating this effect was a challenge.

Small copper tiles, 12 inches squared,

had to be individually covered.

Over 22,000 of these gilded tiles

were then attached to the pagoda,

creating the effect of a single solid gold building.

But this presents a major conservation issue today.

- The use of gold on the Shwedagon Pagoda,

it isn't particularly effective.

I mean, it looks absolutely amazing

and it glistens under the sun,

but it isn't particularly resistant to weather and climate.

So it does need replacing quite regularly.

- [Narrator] The gold leaf flakes off at such a rate,

it actually needs replacing every four to five years,

But this is not a problem at another,

more state of the art, golden building.

The Metrimandir opened in 2008 in Auroville, India.

It's an edifice dedicated to yogic philosophy.

Here, the architects made their tiles

by sandwiching gold leaf between plates of glass,

thus creating a more lasting golden structure.

As goldsmithing spread through the ancient world,

the innovation of ancient engineers

led to even more breakthroughs.

Some of which are still impacting us today.

- A lot of the ingenuity in ancient jewelry

comes in things like how it was fastened together.

And so you start getting some quite interesting techniques

that are fundamental in the history of engineering.

- [Narrator] The chain

and a spring.

Vital in almost every modern industry.

But there's growing evidence to suggest that these,

and other inventions, may owe their origin

to ancient jewelry manufacturing.

- The earliest examples I know of the nut and bolt screw.

Which is fundamental if you want to build a bridge

or a motor car or anything these days.

That dates back to probably late Roman times

when they're using exactly the same principle

as a way to fasten some gold bracelet, the screw thread.

- All these innovations actually

are so crucial to our world today, but they only came about

because they wanted to find new ways of wearing gold.

(dramatic music)

- [Narrator] But the pursuit of gold

has not only been about jewelry and decoration.

The real game changer came with the invention of money.

And it was ancient engineers

who transformed the element of gold

into the world's first coinage currency.

- In the earliest days there wasn't coinage.

I mean, in human history,

it's a relatively late introduction, coinage.

There was obviously barter.

I make a loaf of bread and I swap it

for the person next door's cabbage.

And this sort of thing went on.

- [Narrator] But, as societies became more sophisticated,

bartering systems weren't enough.

- Bartering and exchange is very limited

because it depends on both sides wanting the same thing,

but money itself changes everything

because it has its own intrinsic value.

- [Narrator] Over time, valuable metals started

to become a means of basic exchange.

In Egypt, payments were often made with large gold rings

and some cultures simply used pieces of broken up metal.

But these early currencies had their drawbacks.

- The problem with this was

is that the purity of gold varied,

according to where it had been mined.

It's important to remember that,

when gold is discovered in the ground,

it's never pure, it's always an alloy.

It contains other metals such as silver.

So there was no standardization.

There was no way of guaranteeing

the content of the gold that was being exchanged.

- [Narrator] Most gold in circulation

until the end of the Bronze Age

varied between 70 and 85% purity.

So ancient engineers began to develop

new ways of refining gold to make it pure.

- Now we begin to find references to gold

that's described as gold of one or two times,

or three times in one case.

Because, if you melt gold, a little bit of the other metal

will oxidize and go away.

So every time you melt gold, it gets a little bit purer.

- [Narrator] To confirm a piece of gold's value

before a transaction, various methods

were also devised to check its purity.

One method was a touchstone.

When drawn on with a sample of gold,

these would show a clear streak of color,

which could then be compared to a reliable sample of gold.

Touchstones are quick, easy, and portable

but, as they only check the surface of an object,

they're also limited.

- If the surface has been enhanced, then you'll not find out

what the true composition of the interior is.

- [Narrator] Fire assaying was a more reliable method.

Like refining, it also involved

heating the gold to draw out impurities,

which could determine the actual gold content.

But fire assaying also had drawbacks

as melting it destroyed the original gold object.

Neither method was perfect.

But in approximately 550 BC,

around the time of the ancient Greeks,

in a region of modern day Turkey known as Lydia,

a local ruler in its capital, Sardis, found a solution.

Creating the world's first standardized currency.

Earlier Lydian Kings had created a basic coinage

using electrum, an alloy containing both gold and silver.

But a king called Croesus created a new,

more reliable monetary system

consisting of gold and silver coins

with a standardized purity.

- This was crucial for the development of gold coinage

because you knew exactly how much gold each coin contained.

- At first, Croesus used fairly pure gold

panned in nearby rivers.

But when this ran out, he started to import less pure gold

and turned to his engineers

to find an effective way to refine it.

- He hasn't got any intrinsic, pure gold anymore.

So he has to call in the lads and sort of say,

we've got a problem, we've gotta get to a constant purity.

- [Narrator] In order to remove the silver,

Croesus' engineers developed a more sophisticated

way of refining, known as salt parting.

(dramatic music)

A dry cement of brick dust mixed with salt

was laid inside a pottery container,

thin sheets of impure gold were then laid on top

and layered with the cement until the pot was full.

It was then heated at a low temperature for several days.

During the heating, salt vapors would attack the impure gold

and remove the silver content.

The result, almost 99% pure gold.

Coins were then produced at a set weight

of just under 0.3 ounces.

And with each coin punched with a lion, Lydia's emblem,

this currency could be traded with confidence.

By harnessing money, Croesus became

one of the richest men in the world.

Giving rise to the expression as rich as Croesus

and turning Lydia into the business capital of the world.

- I think Croesus' sort genius, if you like,

was to realize that, if you refine this gold

before you made the coinage, you would have a standard

and other countries would recognize it.

- [Narrator] Over time, coinage allowed bigger

and more sophisticated trading markets to develop.

- The invention of money absolutely transformed society.

It changed the way we go about business.

It changed the way that we relate to each other.

(gentle music)

- [Narrator] The invention of money created

the modern financial world as we know it.

Gold and silver were the basis for currencies

around the planet for centuries.

Nowadays, they have largely been replaced by coins

with lower intrinsic value.

But many countries still have a gold reserve

kept under lock and key just in case.

- It's a finite resource and, in that sense,

it always holds its value.

I mean, in times of political and financial crisis,

that's what you want in your reserves.

You don't want pieces of paper with money stamped on them.

You want bars of gold.

- [Narrator] Today, gold is often exchanged online

by people who have never even seen it.

It's closer to cryptocurrency than real money.

But unlike some crypto coins,

digital gold retains its worth.

While monetary values fluctuate.

But real gold was what counted most in ancient times.

(dramatic music)

For the ancient Romans, gold coinage was vital.

As the empire, expanded the Roman emperors needed money

for a number of reasons, for paying soldiers

and to create a unified empire

trading under a single currency.

But coinage also had another function.

- Coinage became really important as a propaganda tool.

You could actually put your face on the coinage.

And that was so important because it reminded everyone

who was in charge.

- [Narrator] And gold coinage had a very exclusive purpose.

- It's the value of this coin,

which enables the Roman Republic and later,

the Roman emperors to bribe, effectively,

anybody they want to bring within the empire.

- [Narrator] With demand for gold increasing,

the Romans took it from anywhere.

Often seizing it from conquered peoples and melting it down.

But they also came up with inventive ways

to get their hands on greater supplies of gold

from the ground.

In the newly conquered territory

of northwest Spain, at Las Medulas.

Brilliant Roman engineers supercharged their mining.

Using a technique called hushing.

Where water power was used to blast away

vast quantities of earth.

- Water can do a huge amount of damage

to any hillside, mountainside.

You know, its power of pressure, its surge power,

it can destroy large forms of land mass.

Which is, of course, what miners want.

They want to kind of remove all of that material

so you can extract the metal ores.

- [Narrator] To ensure a large enough supply of water,

the Roman engineers used

one of their most famous innovations.

- The Romans were outstanding water engineers,

and one of their finest inventions of all was the aqueduct.

- [Narrator] Aqueducts were vital for Roman cities

transporting fresh water

for drinking, bathing and sanitation.

To ensure a constant flow of water at Las Medulas,

the Romans expertly designed several aqueducts

to transport it from as far away as 90 miles.

Built to hug the contours of the mountains,

they maintained a very gradual downward gradient,

bringing the water to holding tanks

above areas of rich gold deposits.

These aqueducts could deliver between

1.7 and 3.2 billion cubic feet of water a year,

the volume of over 20,000 Olympic swimming pools.

(gentle music)

To reach gold deep inside the rock,

a network of shafts and tunnels would be dug down into it.

And, when all was ready, the sluice gates were opened,

releasing water into the shafts and tunnels.

Which blew the rock face clean off through sheer force.

- The Romans were masters of controlling water.

They understood the volume, the velocity.

They knew exactly how to use it and, in effect,

this is the equivalent of blasting in a modern quarry.

- [Narrator] But the Romans didn't

only use water for mining.

They also used it to pioneer new ways to process gold.

At another ancient Roman gold mine,

in Dolaucothi, west Wales,

a unique monolith has long caused a mystery.

- It's called the Pumsaint Stone, Five Saints Stone,

'cause the story is, you know,

that these five saints, sort of, feeling tired

went to sleep against this stone

and created these five depressions.

- [Narrator] But clues in the surrounding landscape

revealed its possible function.

Telltale water channels and the remains

of a probable water wheel.

Archeologists realized the stone had to be the base

of an early type of trip hammer,

a device used to grind gold bearing rocks.

In order to power a trip hammer,

flowing water would rotate a water wheel,

which in turn drove a cam shaft.

The cam shaft turned rotational movement

into vertical power, driving a series of stamps,

which pounded the rock into tiny pieces

against a stone anvil.

The basis for the modern car engine,

cam shafts were always assumed to be a much later invention.

But the discovery of the Pumsaint Stone

turns that theory on its head.

- Up until its discovery, we always thought

that kind of technology was only around

in the medieval period.

But this stone serves as an anvil

and it dates firmly to the Roman period.

I mean they really were innovators

in the use of water power.

- [Narrator] Such sophisticated methods led to

a massive expansion of the gold industry in Roman times.

- Roman gold mining was of an industrial scale

and you can find it across the entire Roman empire,

all the way from Britain through to Syria

and north Africa, in Greece and Turkey.

- [Narrator] But this came at a great cost.

(gentle music)

The legacy of these hydraulic mining methods

is laid bare in the landscape of Las Medulas.

During its 250 year operation, to reach gold,

the Romans removed almost 18 billion cubic feet of rock.

- The water had been released by the Romans is such velocity

and in such volume, it's carved canyons

through the mountain side.

- [Narrator] This process made Las Medulas

Rome's principle goldmine.

But it devastated the landscape.

It's easy to see why the Romans may have named this

ruina montium, or the wrecking of mountains.

(gentle music)

Today, some modern mining practices can be

just as catastrophic for the environment and for mankind.

Heap leaching is a processing technique using cyanide

to dissolve out particles of gold from its host rock.

It can process millions of tons

of gold laden rock every year,

but it has the potential to cause

devastating environmental issues

as the cyanide is prone to leaking,

polluting rivers and poisoning human water supplies.

Throughout history, we've sought to mine gold

from deeper and deeper underground.

Often at huge human expense.

An ancient technique called fire setting

was used right up to the Middle Ages.

It involved a minor having to light a fire underground,

it's heat would then weaken and crack the rock.

(dramatic music)

But it was dangerous and unpredictable,

often leading to sudden collapse.

An invention of the 19th century

revolutionized mining, dynamite.

The brain child of Swedish chemist, Alfred Nobel,

dynamite used 19th century advances

in chemical engineering to blow apart rock.

It was more controllable than fire setting,

allowing miners to lay the explosives

and then detonate them from a safe distance.

And it allowed them to access more gold than ever before.

Gold mines could now run so deep that, in South Africa,

the miners of the 1886 gold rush

could access the Witwatersrand Basin,

the world's largest known gold field.

These mines have since become

some of the most productive on Earth,

turning Johannesburg into the gold capital of the world,

allowing South Africa to create

the deepest mines on the planet.

- The Mponeng mine in South Africa

is the deepest gold mine in the world.

It is ridiculously deep.

It is four and a half times the height

of the tallest building in the world, the Burj Khalifa.

(dramatic music)

- [Narrator] But such a wealth of gold

has not always been possible to find.

Despite sophisticated mining methods,

gold was still rare and valuable in ancient times.

So, to satisfy high demand,

engineers came up with another solution, gold plating.

To make this, the ancient engineers turned to another metal

with a very unique property, mercury.

Also known as quicksilver, mercury's speed and fluidity

were why the Romans named it after their messenger god.

But it was what happened when it came

into contact with gold which most intrigued them.

- When liquid mercury touches gold,

it literally eats the gold and it binds chemically with it.

- It amalgamates.

So what you wind up with is what is known as

butter of mercury or butter of gold.

- [Narrator] Ancient engineers discovered

that this pliable butter could be used

to coat other cheaper metals like silver or copper.

When heated to 650 degrees Fahrenheit,

the mercury burned away, leaving just the gold,

now bound to the other metal underneath.

- This was the first form of gold plating

and it was so effective that it was widespread

right up until the 19th century.

- [Narrator] But mercury carries many health risks

for those exposed to it.

Nowadays, new, safer and more sophisticated

plating techniques have gradually been introduced.

- Modern gold plating is extraordinary.

It's high science and there's even debate

whether you should actually be able to call it gold plate

'cause there's so little actual gold there.

- [Narrator] These plating advancements means that gold

is now finding brand new applications,

vital ones for our changing world.

It's flexibility and high conductivity

make it a useful material for key electrical components,

like circuit boards and contacts.

- It can be used on connection boards, in SIM cards,

in laptops, in so many devices and gadgets.

- [Narrator] Its ability to be coated very thin

keeps manufacturing costs low,

while it's non corrosiveness means our electronic devices

are less likely to let us down.

- What many people don't realize

is that gold is used in just about

every electronic device that we use today.

So we need gold to live the lives that we lead.

- [Narrator] And, as it's also highly reflective,

such thin gold has become vital for space exploration.

Used since the first men stepped foot on the moon,

it protects sensitive equipment from the sun's radiation.

- It's now possible to get gold so thin

that you can see through it.

So it's even used to coat astronauts' visors.

- [Narrator] And gold's reflectivity

has also made it vital for a very special mission.

(gentle music)

1.69 ounces of the purest gold now coats the mirrors

of the James Webb telescope,

which launched in December, 2021.

- This is not a normal telescope.

This is the most sophisticated engineering you can imagine.

They're going to the very depths of space.

- [Narrator] Gold's exceptional ability to reflect

should allow this honeycomb of mirrors to focus enough light

to image some of the earliest stars ever created.

Perhaps even the very stars which once formed gold itself.

(dramatic music)

Gold has come a long way since ancient peoples

first panned for it in rivers and streams

with their bare hands.

Modern advancements in gold mining and manufacturing

stand on the shoulders of these ancient engineers.

Their innovations have prompted us to dig deeper,

to purify and refine

and to explore gold's infinite possibilities.

Without them, and this most mesmerizing metal,

the world economy, our societies and deep space exploration

may not exist as we know it.

(dramatic music)