Original subtitles

Narrator: the empire state Building in new york --

The world's most Famous skyscraper,

A spectacular icon Of american engineering...

It's amazing what they got done

With the tools They had to work with.

Narrator: ...Upheld by many as The eighth wonder of the world.

♪♪

Today, investigators Explore the secret history

That hides behind Its gleaming facade.

Why is this skyscraper's mast Never used

For its original purpose As an airship station?

We're seeing Very violent motions.

Narrator: and how does it Survive the unforeseen impact

Of an aircraft?

The forces that are created By this sort of an impact

Are immense.

Narrator: To solve these mysteries,

We'll break apart The empire state building's

Limestone walls,

Uncover the Incredible engineering

That supports This super tall skyscraper,

And reveal the secret stories

Hidden within This iconic building.

♪♪

--captions by vitac-- Www.Vitac.Com

Captions paid for by Discovery communications

♪♪

In the heart of manhattan Stands an american icon --

The empire state building,

An engineering wonder Of the modern world.

When it opens in 1931,

It's the tallest building On the planet,

A title it holds For more than 40 years.

♪♪

Today, its sky-piercing outline Is familiar to to billions.

But there are Mysteries concealed

Within this megastructure.

♪♪

Its skin is a wall Of 200,000 cubic feet

Of limestone and granite blocks

And more than 6,500 windows.

♪♪

Inside, 60,000 tons of steel Form a rock-solid backbone

Held together by 100,000 rivets.

73 elevators speed through A combined 7 miles of shafts,

Rising 1,250 feet.

The empire state building Is the first skyscraper

To top 100 stories.

♪♪

What does its Record-breaking height

Reveal about Its forgotten history?

♪♪

New york engineer don friedman

Restores and rebuilds some Of america's oldest structures.

♪♪

Friedman: We're in herald square, Which is one of the busiest

And most crowded parts Of the city,

And there's The empire state building

In front of us at fifth avenue.

♪♪

Narrator: don believes The empire state building's

Distinctive spire sets it apart In the city's crowded skyline.

With that, you go, "Oh. That's the empire state."

Narrator: but this mast Also hides a secret.

In 1929, the architects Set out to construct

A very different building.

Friedman: This is an early drawing.

There's one thing missing here, Which is the spire,

Because this drawing was created

Before the spire Was added to the building.

Narrator: the blueprints reveal That empire state building's

Elaborate spire Is a very late addition.

Engineers shoehorned it Into the design

Only after construction starts.

Why add extra height

To an already Record-breaking building?

♪♪

In 1950, the steel-and-glass Spire starts taking shape.

♪♪

At the top, on floor 102,

An observation deck Offers breathtaking views.

One floor above Is a strange balcony,

With a knee-high wall As the only barrier

To a 1,250-foot drop.

The architects declare that this Is for giant airships to dock

And unload passengers directly Into the empire state building.

But is this the real reason For the spire?

♪♪

In the early 1930s, docking And airship with a skyscraper

Is a radical new idea.

Airships don't need runways.

They attach to towers Or masts using ropes.

Forward-thinking building Designers place mooring points

On the top of their buildings

In preparation for a future Of airship-filled skies.

♪♪

In 1931, airships try to dock

At the empire state Building's spire.

It's such a jaw-dropping site, Crowds block the sidewalks

And the busy streets below.

One airship clings on For 3 minutes.

Another drops a bundle Of newspapers.

No passengers disembark,

And this achievement Is never replicated.

Why is this airship The only one to dock

At the empire state building?

Civil engineer Maarten van reeuwijk

Thinks he knows the answer.

He's investigating The empire state building's

Forgotten airship port.

He's recreating the conditions Faced by the docking airship

In this wind tunnel At imperial college london.

Maarten wants to find out if an Airship could offload passengers

At the top of the world's Tallest building.

What I have here is a balloon, Which is filled with helium,

And this is going to be A very rough approximation

To the airship, And what I'm going to do is,

I'm going to moor this airship

On the top of the building Right here.

Narrator: first, The tunnel's fans start up.

♪♪

Maarten adds smoke to track Where the wind goes.

♪♪

So here, you can see the flow As it goes around this airship.

Narrator: the wind that hits The top of the building

Must go somewhere.

It deflects to The building's sides,

But it also goes up.

You see that this highly Unsteady flow in the wake

Causes huge response From our airship.

Narrator: the airship And all its furniture, luggage,

And passengers would be Hurled around inside.

Van reeuwijk: we're seeing very Violent motions of the airship.

Full-scale, these would be Ups and downs of the airship

Of 10, 20 meters.

This would be hugely dangerous.

Narrator: Mooring an airship to a high Mast takes considerable skill.

Even at ground level, it can Be a treacherous maneuver.

This is the uss los angeles.

In 1926, a shift in temperature At ground level causes warm air

To flip the airship Vertically on its moorings.

Luckily, no one is onboard.

It's not the greatest of ideas To try to moor an airship

On a building like The empire state building.

♪♪

Narrator: tall structures Like skyscrapers

Generate strong updrafts of wind And unpredictable gusts.

♪♪

To stop moored airships From tipping up in the updrafts,

They need a second tether To hold their tails in place.

♪♪

The tail tether can rotate,

Allowing the airship to align With gusting winds.

But the empire state building Doesn't have this mechanism.

Any airship can only moor For a few minutes

Or drop a bundle of newspapers Before moving on.

♪♪

Tethered precariously just To the mast of the skyscraper,

This is all they can Safely achieve.

In 1931, the world's Top airship captain,

Germany's hugo eckener, Visits new york.

He concludes that any attempt To drop off passengers

At the empire state building Would end in disaster.

A few years later, the explosion Of the nazi airship hindenburg

Underlines the dangers.

♪♪

Man: the world's largest And most luxurious airship,

The hindenburg,

Burns in a disaster.[ crowd screaming ]

This tragedy dramatically ends A future era of airship travel.

♪♪

Narrator: don believes The real reason for the mast

Lies with an intense rivalry That grips the city.

People were building taller

And taller buildings In new york.

Chrysler building was the Tallest building in the world

For about a year.

By adding the spire onto The empire state building,

It went up about Another 15 stories in height.

Narrator: the spire allows The empire state building

To soar above its rivals,

And it protects its title Far into the future.

Friedman: Any publicity will help,

And constructing the tallest Building in the world

Is one way to get A lot of free publicity.

♪♪

Narrator: The plans for an airship station

Might have been unrealistic,

But the empire state building is Still a revolutionary structure.

For a building to climb 1,200 Feet tall today is astonishing.

To reach such heights 90 years ago

In the middle of the great Depression is truly incredible.

How do the empire State's engineers

Achieve this seemingly Impossible feat

And successfully support the Massive, 365,000-ton building?

Narrator: The empire state building --

The world's most Iconic skyscraper.

For 90 years, it's been towering Over the streets of manhattan.

It's a true Skyscraping colossus,

Weighing in at 365,000 tons.

Why does this Stone-and-steel monster

Not sink into the ground?

The empire state building

Is actually a slender Stepped pyramid,

Widening towards the bottom.

This ingenious shape spreads The weight of the tower

Across more than 80,000 square feet.

♪♪

Beneath the surface, Sturdy steel columns

Firmly lock into huge foundation Shafts of solid concrete.

♪♪

This base is just Three stories deep,

52 feet,

A fraction of the tower's Total height.

How can such shallow foundations Support such a massive building?

♪♪

Geotechnical engineer Andrew klaetsch

Thinks the secret Lies deep under new york city.

♪♪

He's at a construction site

For manhattan's newest Supertall skyscraper.

They are excavating right now To build their foundations.

Narrator: Andrew only has to descend 10 feet below street level

To hit the city's bedrock.

And right here is the very Surface of the bedrock today,

Right below 32nd street.

Narrator: The empire state building

Weighs 365,000 tons.

Similar skyscrapers in london, Tokyo, and chicago

Have foundations That are twice as deep,

But new york stands On firmer ground.

Well, what you see here Is this rock

That was once buried At great depth

And formed under Enormous pressure.

♪♪

Narrator: This gray rock is called schist.

It reflects the light.

Klaetsch: It actually looks like glitter,

And that is the mica minerals In the manhattan schist.

♪♪

Narrator: manhattan schist forms 450 million years ago

When two continental Plates collide,

Pushing up vast mountain ranges.

♪♪

Over millions of years,

The rocks on the surface Wear away,

Exposing incredible, strong Cores of compressed schist

That manhattan stands on today.

♪♪

To find out how strong This manhattan rock is,

Andrew takes a sample To his lab.

He uses a compression machine To investigate

How much pressure This stone can withstand.

♪♪

Much stronger.

Andrew's colleague lysandra Applies increasing pressure

To this 2-inch-thick Manhattan schist.

This is the load As it increases with time,

We're only up to Just over 40,000 pounds.

The sample Is holding strong.

Almost 60,000 pounds.

[ boom ]Whoa.

[ laughs ]

That was pretty good, Pretty explosive.

So you can see, it shattered Into many pieces.

♪♪

This manhattan schist Can withstand

A staggering 75,000 pounds Of pressure per square inch.

That's over 100 times More pressure

Than is required for a structure Like the empire state building.

It's exceptionally strong.

It's significantly higher Than any sort of pressure

That we'd be looking at in terms Of building foundations.

♪♪

Narrator: This incredibly tough schist Means the empire state building

Can be firmly anchored In just a few feet of bedrock,

But it also presents a problem.

It takes months to excavate Enough of the tough rock

To anchor just A shallow foundation.

Construction starts Almost immediately

After the wall street crash Of 1929.

Money's tight, and time spent Digging schist means more cost.

♪♪

Fortunately, the architects find That someone else

Has already done The job for them.

♪♪

As builders demolish The old waldorf astoria hotel

That stands on the chosen site,

They uncover foundations Already 40 feet deep.

♪♪

So they must only drive Their piles 15 feet deeper

To securely anchor The metal skeleton

Of the empire state building.

♪♪

These preexisting foundations Save dollars

And give the builders A flying start.

♪♪

Once the construction Reaches ground level,

The entire structure Goes from start to finish

In just 7 months.

It's an astonishing achievement.

How is this Record-breaking structure

Built at such great speed And why?

Narrator: in 1930, Construction workers finish

The three-story-deep foundations

Of the new empire State building.

With a head start From existing foundations,

It takes them 6 months To get this far,

But the hard part Is only just beginning.

They now have to construct The tallest building in history,

And the longer it takes, The more money it will cost.

♪♪

The steel frame Is the key innovation

Of the skyscraper age.

It allows the empire State building's team

To build At death-defying heights.

But the breakneck speed Of the construction

Is due to another miracle Of modern engineering.

♪♪

"I"-shaped steel beams Form the skeleton

Of the entire tower.

Thousands of rivets Bolt them together...

♪♪

...Creating a massive Three-dimensional frame

Of steel boxes.

♪♪

The builders simply hang The stone facade

Onto the outside like a curtain.

♪♪

They repeat the same pattern

For floor after floor After floor.

♪♪

Building nearly a story a day,

They take just 7 months To reach 1,250 feet.

♪♪

Engineer don friedman

Works with experienced Metalworker rich bauer

At a steel forge in new jersey To explore

How the empire state building's Steel construction kit

Is pieced together On-site so fast.

Well, right now, We're heating up the rivet

And making sure It gets extremely hot.

Narrator: Rich thinks the humble rivet

Is the real hero Of the empire state building.

Bauer: once you send it All the way home

And make the rivet Completely up,

It's not like a nut or a bolt

That's going to loosen up Or rattle over time.

Welds could crack.

Rivets, once they cool off, It contracts.

It makes sure that joint Is completely tight.

♪♪

You want a nice, Consistent orange.

Narrator: the rivet comes out Of the furnace red-hot,

But it takes just seconds For the metal

To become too cool to work.

Bauer: I couldn't set this rivet now.

We'd have to throw That rivet out

And start it over And try another rivet.

Narrator: from the furnace In the workshop,

It takes three people To set a single, red-hot rivet

Before it cools.

The construction of The empire state building

Requires an astonishing level Of coordination and teamwork.

It's the first time don has seen This process in action.

Friedman: I've read about it, but it's Something else seeing it.

Installing rivets Requires a team of people

Working together very closely

To make sure That everything happens

Before the rivets cool off.

Narrator: this fast cooling Poses a huge challenge

To workers at the empire State building.

They need more than 100,000 rivets

To hold the steel Girders together.

To heat the rivets, engineers Build furnaces on each floor,

But still, the raw-steel beams Can be more than 35 feet away.

Incredibly, workers Throw the rivets.

♪♪

They were trying To throw these rivets

10, 15, 20, 30 feet Up in the air,

And they had to make sure They do this

All before it cooled off.

Narrator: throwing hot rivets Solves a problem,

But it's very dangerous.

It took enough skill to do this, And you think about doing it

In the circumstances of actually Building a high-rise building,

And it's just incredible.

Narrator: Hot riveting is key to The strong and fast construction

Of the empire state building.

It is built like Prefabricated furniture,

A 60,000-ton made-to-order Metal framework

Assembled simply on-site.

And as soon as this Basic framework is complete,

Other teams Can finish each floor.

♪♪

Workers fill temporary Wooden floors with concrete

And reinforce them With wire mesh.

♪♪

As soon as the floor is set, They lay down railway tracks

To move materials quickly from Elevators to the outer edges.

♪♪

Other teams construct Makeshift cafeterias

On the uppermost floors

So builders don't waste time Going to the bottom to eat.

♪♪

Finally, workers at the top Simply hang the external walls

On the steel skeleton.

The building soars At a lightning-quick pace.

The empire state building Takes less than 14 months

To build, completing in 1931.

President hoover Turns the lights on

From the white house In a spectacular ceremony.

♪♪

But by building higher Than anyone else in history,

The architects face A new problem --

Hurricanes.

The empire state building Will soon be tested

By one of the mother nature's Most destructive forces.

Narrator: new york's iconic Empire state building

Towers over manhattan,

Just as it has for 90 years.

These 103 stories of glass, Stone, and steel

Face an invisible And unpredictable threat --

Hurricane-force winds.

♪♪

Research scientist mark arend

Tracks the wind speeds Over manhattan

From the city college Of new york's weather station.

Arend: so, we're on top Of a tall building,

About 5 miles from The empire state building

And midtown manhattan.

Narrator: his research Investigates the wind patterns

Flowing across the city.

♪♪

Manhattan, perched By the atlantic coast,

Is exposed to nature's worst.

Arend: there have been A number of hurricanes

That have actually hit manhattan

And caused a lot of damage.

♪♪

Narrator: the top of The empire state building

Faces a battering ram Of pressure from all directions.

To understand The threat it faces,

Mark analyzes measurements Recorded over the last 10 years.

We've taken data From various weather stations

That are located on the ground In the new york city metro area.

Up here in central park, 89 miles per hour.

It was a maximum 3-second wind gust.

Down here in Midtown manhattan --

41 miles per hour.

Narrator: But powerful gusts of wind Are only part of the problem.

In midtown manhattan,

The huge concentration Of tall buildings disrupts wind.

Avenues of skyscrapers Act like vast wind tunnels,

Funneling and amplifying The wind to dangerous speeds.

You have very tall buildings.

That creates a lot of turbulence

And makes the wind Very difficult to measure.

Narrator: how does The empire state building

Stay upright in these Phenomenal wind conditions?

The force of the wind pushing Onto the facade can be immense,

But the rigid stone Stays firm.

It channels The wind energy inside

To the steel frame within.

At its heart is a backbone

Reinforced with diagonal Steel cross braces.

♪♪

They're encased In solid concrete

That is not only strong But incredibly stiff.

Together, the steel and concrete Form a rock-solid core,

But can this 1930s technology Stop the tower swaying violently

In today's Hurricane-force winds?

♪♪

Don friedman examines How new york's skyscrapers

Behave in extreme conditions.

Friedman: There are actually buildings Pretty much all over the place

That are famous for being A little too limber in the wind.

Narrator: a badly designed Skyscraper will result

In disastrous damage And collapse.

Don and his colleague shaquana

Model the empire state Building's inner steel skeleton.

Okay. So, let's take a look At this model.

So we did a comparison of A moving frame of a building.

One is without Any cross bracing.

Narrator: As the wind speed increases,

The model building Starts to move.

Over here on this screen, We have the cross bracing,

Which you can see Is a drastic difference

In how the building Behaves altogether.

Wind clearly affects the two Frames in different ways.

Friedman: What the simple models show

Is that the addition Of cross bracing

Reduces the side sway Under wind load

To about 1/8 Of what it previously was.

And people notice When buildings move too much.

Narrator: cross bracing gives Stability to simple structures

And supertall skyscrapers.

It reduces any sideways Movement dramatically.

This simple But effective engineering

Solves a potentially Catastrophic problem

For the empire state building.

The old buildings Were very well-designed,

Even with the more Primitive tools.

Narrator: with access To today's computer models,

The building's engineers Might have found

A very different solution.

♪♪

As wind rushes around A skyscraper,

It creates swirling eddies that Push the tower side to side,

Making it sway dangerously.

So modern, supertall skyscrapers

Are designed With ingenious profiles

That disrupt the wind And stop the sway.

♪♪

Some buildings,

Like the super skinny Park avenue tower in new york,

Have holes to simply Let the wind pass through.

♪♪

Other have mass dampers inside,

Huge traveling weights that Counteract the swaying force

And keep the building steady.

♪♪

The empire state building Is a textbook example

Of solid engineering,

Built to withstand everything That nature can throw at it.

But in 1945, a totally Unexpected force strikes it,

One engineers couldn't foresee.

Narrator: on july 28, 1945,

Disaster strikes The empire state building.

A b-25 bomber With three crewmen onboard

Is on a routine transport flight

From an army base In massachusetts.

It's flying over manhattan,

Headed for newark airport Just across the city.

The weather is relatively bad. The visibility is poor.

There's fog across manhattan.

Narrator: what happens next Has no warning.

Traveling at over 200 miles an hour,

The bomber flies straight At the empire state building.

♪♪

It tears A 250-foot-square-foot hole

In the 79th floor,

Carving a path of destruction,

Starting fires,

And snapping elevator cables.

One engine rips through The entire building

And breaks through The opposite wall.

♪♪

The other engine tumbles down An elevator shaft,

Falling 1,000 feet To the subbasement.

How does the empire State building

Survive this Catastrophic accident?

Engineer adrian bruegger

Explores this Engineering mystery.

Bruegger: the bomber pierces Through the facade.

It's an immense impact,

Like getting punched By a sledgehammer.

♪♪

Narrator: the b-25 mitchell Bomber is a formidable machine.

It weighs up to 35,000 pounds

And flies at nearly 300 miles per hour.

It strikes the north wall

With an immense Amount of energy.

How is it that people inside the Building survive this disaster?

Steel beams make up the skeleton Of the empire state building.

Adrian wants to test what force Of impact they can withstand.

♪♪

Bruegger: What you see here is a beam

Like you would find In the floor joists

Or the floor beams Of the empire state building,

And it would hold up the floors.

What we will see is How much ductility,

How much ability this steel has

To actually deform Before it breaks.

Narrator: adrian applies 3 tons Of force to the steel beam.

♪♪

Bruegger: so now we are Pushing on the beam still,

And you can see that It's deflecting very heavily.

[ metal creaks ]

Something moved a little?

But we're okay. We can keep going.

Narrator: as adrian increases The weight load to 3.9 tons,

The steel beam Is still holding strong.

Bruegger: so you can see, This is absolutely amazing.

The beam is completely Deformed in the middle,

But it's still holding almost 4 tons of spring energy.

It looks like it failed,

But it's actually Still doing its work.

Narrator: this steel has An incredible ductility.

It can bend in half Before it snaps.

A photo of the impact The b-25 makes on the building

Proves the incredible strength Of the beams.

♪♪

Bruegger: Here, you can see these beams

Look very much like What we have here.

They're mangled.

They're twisted, But they're not broken,

And that's important. They're not fractured,

So they stayed in place, And that's key.

Narrator: the steel beams Are bent, not broken.

The structure survives The main force

Of the initial impact.

Many escape.

Others are rescued By first responders.

14 people die In the tragic accident.

[ indistinct conversations ]

But there is a miraculous Survival story.

Astonishingly, the structure Saves someone's life.

♪♪

[ elevator bell dings ]

20-year-old betty lou oliver Is an elevator operator.

She's blasted Out of her elevator car

On the 80th floor When the plane hits.

Onlookers hurry her into another Car to get her to safety.

But as the doors close, The cable snaps,

And the car instantly drops.

As betty lou's car Picks up speed,

The emergency brakes fail.

But trapped air Compresses in the shaft,

Slowing her fall.

And at the bottom,

The severed cable forms a coil That cushions the impact.

Miraculously, betty lou survives

Falling 1,000 feet.

The empire state building Survives the plane crash, too.

But the moment of impact causes Another potential lethal risk

To the structure And life inside.

The plane's fuel Ignites disastrously.

Man: These exclusive motion pictures Show the empire state building

Burning like A great smoky torch

With flames bursting From the windows.

♪♪

Narrator: fire and skyscrapers Can be a deadly combination,

But how does The building survive?

♪♪

Adrian wants to find out How the empire state building's

Steel skeleton stands up To the flames and intense heat

To save the people inside.

It's quite sharp.

Thanks.

Bruegger: what we are doing here Is a good simulation

Of what you would expect To happen

In, for example, a hydrocarbon Fire due to an airplane crash.

♪♪

Narrator: he heats the steel To find its breaking point.

♪♪

Bruegger: go. Go more.

[ gas hissing ]

There you go. That's it.

Narrator: As the steel is heated,

A machine pulls from both ends With increasing force.

Steel melts At 2,500 degrees fahrenheit,

But just a fraction Of that temperature

Is enough to seriously Weaken the metal.

♪♪

[ steel snaps ]

Bruegger: there it is.

It's actually about 420 degrees celsius.

Narrator: the fire from The exploding bomber

Will quickly rage To double this temperature.

The integrity of the empire State building's steel skeleton

Will easily fail With the heat of a fire.

It's vital the flames are put Out before the skeleton fails

And the building crashes.

Bruegger: Fire does weaken the steel.

This is the achilles' Heel of steel.

♪♪

Narrator: the empire state Building's designers know

That fire could bring An entire skyscraper down,

So they build in A hidden safety feature --

Standpipes.

These rigid vertical pipes Move water

To the top of very tall Buildings at great speed.

A standpipe acts like A fire hydrant at height.

Pernal: it provides water To the firefighters,

Who can hook up their hoses In the stairwell

And fight the fires Out on the floors.

Narrator: fire safety officer Matt pernal checks standpipes

In new york's Tallest skyscrapers.

The empire state building's Standpipe system

Consists of an impressive 7,340 feet of pipe

And 6 miles of hose.

♪♪

All right, jose. We're set up down here.

I'm going to go ahead And get the churn test started.

♪♪

We were able to reach The 500 gallons per minute.

The pump is putting out Enough flow and pressure

In order to reach The roof level,

And that will help the Firefighters put out the fire.

♪♪

Narrator: in 1945, fire crews Use the same standpipe system

To quickly extinguish the blaze In the empire state building.

The flames are out Within 40 minutes,

Saving the metal from Lethal structural damage

And allowing it to reopen For business

Just two days after the crash,

With tens of thousands of people Returning to work inside.

♪♪

The empire state building's Colossal structure

Can absorb the impact Of a world war ii bomber.

It can also survive Hurricane-force winds.

How does its gleaming facade Stand up to the test of time?

Narrator: new york's empire State building is such an icon,

It's been called An eighth wonder of the world.

Its gleaming facade is built From an extraordinary material.

At the time of construction, Many skyscrapers are coated

In a layer of brick And ceramic terra-cotta.

The empire state building Is covered in limestone,

The same stone As ancient wonders --

The 4,500-year-old Egyptian pyramids...

♪♪

...And the 2,000-year-old Roman colosseum.

But what is the secret To its gleaming facade?

Geologist polly sturgeon Traces the stone to its source

To explore why Architects choose it.

This is the empire quarry In indiana.

In the 1920s, they were pulling Several hundred million tons

Of limestone out Of this small stretch of land.

Narrator: The limestone used to cover the Empire state building's facade

Can only be found in this Small area of the united states.

Sturgeon: it's right in the Heart of the indiana stone belt,

This narrow 30-mile Stretch of land,

Which has produced up to 75%

Of all limestone buildings In north america.

♪♪

Narrator: The indiana limestone is used

In many of the country's Most important buildings,

Like the pentagon

And the lincoln memorial.

What makes it so sought-after?

♪♪

Polly compares stone cores Taken from test sites

Across the indiana Limestone belt.

Sturgeon: so, this is The indiana limestone.

You can see it's a nice, Even color and texture.

Narrator: layers of tiny crushed Prehistoric sea creatures

Make up the limestone.

They give the rock Its fine grain structure.

There's no large shells Sticking out or holes in it,

And that's because Of the ocean environment

That we had 340 million Years ago here in indiana.

Waves would break all Of those dead-animal body parts

Into a nice, even size.

Makes it excite for carving And putting on buildings.

♪♪

Narrator: workers can extract Limestone from this quarry

In 3-ton, perfectly formed Blocks without any faults.

♪♪

Gang saws then slice the stone Into smaller pieces.

Other popular building stones Like granite or marble,

You can have areas Of irregularity

With those veins that make it Difficult to carve large pieces.

Narrator: the limestone can be Cut and carved in any direction

Without cracking.

It's ideal for cutting the Identical decorative details

That are seen in the facade Of the empire state building.

♪♪

Its faultless, Fine-grain structure

Appears to be the perfect Building material.

But limestone has one Potentially serious flaw.

It dissolves in rainwater.

Limestone can weather away And be dissolved.

Chemically, all of our rainwater Is slightly acidic,

So it does eat away at the rock.

Narrator: polly uses diluted Hydrochloric acid

To demonstrate the effect It has on the stone.

I can put it on there,

And you can see That it fizzes very rapidly,

And because the indiana Limestone is so high in calcite,

It always reacts Very vividly like this.

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Narrator: new york's acidic Rainwater is slowly eating away

At the facade Of the empire state building.

But the indiana limestone Is so durable

That it takes A staggering 60 years

Before any work is needed

To repair or replace the stone Covering the skyscraper.

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Meticulous cleaning And renovation

Ensures the limestone layer Will never dissolve or crumble,

Meaning this modern wonder Can survive

As long as the Ancient wonders of the world.

The empire state building Is an incredible achievement.

It's the first structure To top 100 stories,

A pioneering icon paving the way To ever taller skyscrapers.

It's extremely resilient, With innovative engineering

And farsighted use of materials.

This incredible building Will stand firm

In manhattan's skyline For centuries to come.

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