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00:02the Empire State Building in New York the world's most famous skyscraper a spectacular icon of
00:11American engineering it's amazing what they got done with the tools they had to work with
00:18upheld by many as the eighth wonder of the world
00:25today investigators explore the secret history that hides behind its gleaming facade why is this
00:32skyscrapers mast never used for its original purpose as an airship station we've seen very
00:38violent motion and how does it survive the unforeseen impact of an aircraft the forces
00:45that are created by this sort of an impact are immense to solve these mysteries we'll break
00:53apart the Empire State Building's limestone walls uncover the incredible engineering that supports
01:00this super tall skyscraper and reveal the secret stories hidden within this iconic building
01:19in the heart of Manhattan stands an American icon the Empire State Building an engineering wonder of
01:28the modern world when it opens in 1931 it's the tallest building on the planet a title it holds for
01:38more
01:39than 40 years today its sky piercing outline is familiar to billions but there are mysteries concealed
01:50within this megastructure its skin is a wall of 200,000 cubic feet of limestone and granite blocks and
02:01more than six and a half thousand windows
02:07inside 60,000 tons of steel form a rock-solid backbone held together by 100,000 rivets 73 elevators speed
02:19through
02:20a combined seven miles of shafts rising 1250 feet the Empire State Building is the first skyscraper to top 100
02:30stories what does its record-breaking height reveal about its forgotten history
02:39New York engineer Don Friedman restores and rebuilds some of America's oldest structures
02:50we're in Herald Square which is one of the busiest and most crowded parts of the city
02:54and there's the Empire State Building in front of us at Fifth Avenue
02:59Don believes the Empire State Building's distinctive spire sets it apart in the city's crowded skyline
03:06with that you go oh that's the Empire State but this mast also hides a secret
03:14in 1929 the architects set out to construct a very different building this is an early drawing
03:21there's one thing missing here which is the spire because this drawing was created before the spire was added to
03:26the building
03:28the blueprints reveal that the Empire State Building's elaborate spire is a very late addition
03:35engineers shoehorned into the design only after construction starts
03:41why add extra height to an already record-breaking building
03:50in 1950 the steel and glass spire starts taking shape
03:58at the top on floor 102 an observation deck offers breathtaking views
04:09one floor above is a strange balcony
04:13with a knee-high wall as the only barrier to a 1250 foot drop
04:19the architects declare that this is for giant airships to dock and unload passengers
04:25directly into the Empire State Building but is this the real reason for the spire
04:33in the early 1930s docking an airship with a skyscraper is a radical new idea
04:40airships don't need runways they attach to towers or masts using ropes
04:45forward-thinking building designers place mooring points on the top of their buildings
04:50in preparation for a future of airship filled skies
04:57in 1931 airships try to dock at the Empire State Building spire it's such a jaw-dropping sight
05:06crowds block the sidewalks in the busy streets below one airship clings on for three minutes
05:13another drops a bundle of newspapers no passengers disembark and this achievement is never replicated
05:21why is this airship the only one to dock at the Empire State Building
05:28civil engineer Martin Van Rewijk thinks he knows the answer
05:33he's investigating the Empire State Building's forgotten airship port
05:39he's recreating the conditions faced by the docking airship
05:43in this wind tunnel at Imperial College London
05:48Martin wants to find out if an airship could offload passengers at the top of the world's tallest building
05:55what I have here is a balloon which is filled with helium
05:59and this is going to be a very rough approximation to the airship
06:03and what I'm going to do is I'm going to moor this airship on the top of the building right
06:09here
06:10first the tunnel's fans start up
06:15Martin adds smoke to track where the wind goes
06:20so here you can see the flow as it goes around this airship
06:24the wind that hits the top of the building must go somewhere
06:30it deflects to the building's sides
06:32but it also goes up
06:35you see that this highly unsteady flow in the wake
06:39causes huge response from our airship
06:44the airship and all its furniture, luggage and passengers would be hurled around inside
06:51we're seeing very violent motions of the airship
06:54full scale these would be ups and downs of the airship of 10-20 meters
06:59this would be hugely dangerous
07:03mooring an airship to a high mast takes considerable skill
07:07even at ground level it can be a treacherous maneuver
07:12this is the USS Los Angeles
07:15in 1926 a shift in temperature at ground level causes warm air to flip the airship vertically on its moorings
07:23luckily no one is on board
07:25it's not the greatest of ideas to try to moor an airship on a building like the Empire State Building
07:37tall structures like skyscrapers
07:41generate strong updrafts of wind and unpredictable gusts
07:48to stop moored airships from tipping up in the updrafts
07:53they need a second tether to hold their tails in place
07:59the tail tether can rotate
08:01allowing the airship to align with gusting winds
08:05but the Empire State Building doesn't have this mechanism
08:10any airship can only moor for a few minutes
08:14or drop a bundle of newspapers before moving on
08:22tethered precariously just to the mast of the skyscraper
08:26this is all they can safely achieve
08:30in 1931
08:31the world's top airship captain
08:34Germany's Hugo Eckner visits New York
08:38he concludes that any attempt to drop off passengers at the Empire State Building would end in disaster
08:45a few years later the explosion of the Nazi airship Hindenburg underlines the dangers
08:53the world's largest and most luxurious airship
08:57the Hindenburg burns in a disaster
09:00this tragedy dramatically ends a future era of airship travel
09:09Don believes the real reason for the mast lies with an intense rivalry that grips the city
09:16people were building taller and taller buildings in New York
09:19Chrysler Building was the tallest building in the world for about a year
09:22by adding the spire onto the Empire State Building it went up about another 15 stories in height
09:28the spire allows the Empire State Building to soar above its rivals
09:33and it protects its title far into the future
09:37any publicity will help and constructing the tallest building in the world is one way to get a lot of
09:42free publicity
09:47the plans for an airship station might have been unrealistic
09:50but the Empire State Building is still a revolutionary structure
09:56for a building to climb 1200 feet tall today is astonishing
10:01to reach such heights 90 years ago
10:04in the middle of the Great Depression is truly incredible
10:08how do the Empire State engineers achieve this seemingly impossible feat?
10:15and successfully support the massive 365,000-ton building?
10:34the Empire State Building
10:36the Empire State Building
10:36the world's most iconic skyscraper
10:39for 90 years it's been towering over the streets of Manhattan
10:45it's a true skyscraping colossus
10:47weighing in at 365,000 tons
10:52why does this stone and steel monster not sink into the ground?
10:57the Empire State Building is actually a slender stepped pyramid
11:02widening towards the bottom
11:04this ingenious shape
11:06spreads the weight of the tower across more than 80,000 square feet
11:14beneath the surface
11:16sturdy steel columns
11:18firmly lock into huge foundation shafts of solid concrete
11:25this base is just three stories deep
11:2852 feet
11:31a fraction of the tower's total height
11:34how can such shallow foundations support such a massive building?
11:43geotechnical engineer Andrew Kleitsch
11:45geotechnical engineer Andrew Kleitsch thinks the secret lies deep under New York City
11:50he's at a construction site for Manhattan's newest super tall skyscraper
11:55they are excavating right now to build their foundations
11:59Andrew only has to descend 10 feet below street level to hit the city's bedrock
12:06and right here is the very surface of the bedrock today
12:10right below 32nd street
12:14the Empire State Building weighs 365,000 tons
12:20similar skyscrapers in London, Tokyo, and Chicago
12:26have foundations that are twice as deep
12:30but New York stands on firmer ground
12:33what you see here is this rock that was once buried at great depth
12:38and formed under enormous pressure
12:44this grey rock is called schist
12:48it reflects the light
12:50it actually looks like glitter
12:52and that is the mica minerals in the Manhattan schist
13:00Manhattan schist forms 450 million years ago
13:04when two continental plates collide
13:07pushing up vast mountain ranges
13:12over millions of years the rocks on the surface wear away
13:15exposing incredible strong cores of compressed schist
13:19that Manhattan stands on today
13:23to find out how strong this Manhattan rock is
13:27Andrew takes a sample to his lab
13:30he uses a compression machine to investigate how much pressure this stone can withstand
13:38much stronger
13:39Andrew's colleague Lissandra
13:42applies increasing pressure to this 2 inch thick Manhattan schist
13:46this is the load as it increases with time
13:48and we have to just over 40,000 pounds
13:51the sample is holding strong
13:54almost 60,000 pounds
14:03that was pretty good, pretty explosive
14:06as you can see it shattered into many pieces
14:13this Manhattan schist can withstand a staggering 75,000 pounds of pressure per square inch
14:20that's over a hundred times more pressure than is required for a structure like the Empire State Building
14:26it's exceptionally strong
14:29it's significantly higher than any sort of pressure that we'd be looking at in terms of building foundations
14:39this incredibly tough schist means the Empire State Building can be firmly anchored in just a few feet of bedrock
14:46but it also presents a problem
14:49it takes months to excavate enough of the tough rock to anchor just a shallow foundation
14:56construction starts almost immediately after the Wall Street Crash of 1929
15:01money's tight and time spent digging schist means more cost
15:08fortunately, the architects find that someone else has already done the job for them
15:16as builders demolish the old Waldorf Astoria Hotel that stands on the chosen site
15:21they uncover foundations already 40 feet deep
15:27so they must only drive their piles 15 feet deeper
15:31to securely anchor the metal skeleton of the Empire State Building
15:37these pre-existing foundations save dollars and give the builders a flying start
15:45once the construction reaches ground level
15:47the entire structure goes from start to finish in just seven months
15:52it's an astonishing achievement
15:55how is this record-breaking structure built at such great speed
15:59and why?
16:16in 1930 construction workers finished the three-story deep foundations of the new Empire State Building
16:24with a head start from existing foundations it takes them six months to get this far
16:31but the hard part is only just beginning
16:33they now have to construct the tallest building in history
16:38and the longer it takes, the more money it will cost
16:43the steel frame is the key innovation of the skyscraper age
16:48it allows the Empire State Building's team to build at death-defying heights
16:54but the breakneck speed of the construction is due to another miracle of modern engineering
17:03I-shaped steel beams form the skeleton of the entire tower
17:09thousands of rivets bolt them together
17:16creating a massive three-dimensional frame of steel boxes
17:22the builders simply hang the stone facade onto the outside
17:27like a curtain
17:31they repeat the same pattern for floor after floor after floor
17:38building nearly a story a day
17:41they take just seven months to reach 1250 feet
17:47engineer Don Friedman works with experienced metal worker Rich Bower at a steel forge in New Jersey
17:53to explore how the Empire State Building steel construction kit is pieced together on site so fast
18:01well right now we're heating up the rivet and making sure that it gets extremely hot
18:06Rich thinks the humble rivet is the real hero of the Empire State Building
18:13once you send it all the way home and make the rivet completely up
18:16it's not like a nut or a bolt that's going to loosen up or rattle over time
18:21welds could crack, rivets, once they cool off, it contracts
18:25you can make sure that joint is completely tight
18:31you want a nice consistent orange
18:35the rivet comes out of the furnace red hot
18:38but it takes just seconds for the metal to become too cool to work
18:42I couldn't set this rivet now
18:44we'd have to throw that rivet out
18:46we'll start it over and try another rivet
18:48from the furnace in the workshop it takes three people to set a single red hot rivet before it cools
18:55the construction of the Empire State Building requires an astonishing level of coordination and teamwork
19:01it's the first time Don has seen this process in action
19:05I've read about it but it's something else seeing it
19:08installing rivets requires a team of people working together very closely
19:12to make sure that everything happens before the rivets cool off
19:17this fast cooling poses a huge challenge to workers at the Empire State Building
19:23they need more than 100,000 rivets to hold the steel girders together
19:28to heat the rivets engineers build furnaces on each floor
19:32but still the raw steel beams can be more than 35 feet away
19:38incredibly workers throw the rivets
19:43they were trying to throw these rivets 10, 15, 20, 30 feet up in the air
19:49and they had to make sure they do this all before it cooled off
19:53throwing hot rivets solves a problem
19:55but it's very dangerous
19:59it took enough skill to do this and you think about doing it in the circumstances of actually building a
20:03high-rise building
20:04and it's just incredible
20:07hot riveting is key to the strong and fast construction of the Empire State Building
20:12it is built like prefabricated furniture
20:15a 60,000-ton made-to-order metal framework assembled simply on site
20:21and as soon as this basic framework is complete other teams can finish each floor
20:30workers fill temporary wooden floors with concrete
20:34and reinforce them with wire mesh
20:41as soon as the floor is set they lay down railway tracks
20:46to move materials quickly from elevators to the outer edges
20:53other teams construct makeshift cafeterias on the uppermost floors
20:57so builders don't waste time going to the bottom to eat
21:02finally workers at the top simply hang the external walls on the steel skeleton
21:09the building soars at a lightning quick pace
21:14the Empire State Building takes less than 14 months to build
21:18completing in 1931
21:21President Hoover turns the lights on from the White House in a spectacular ceremony
21:28but by building higher than anyone else in history
21:31the architects face a new problem
21:36hurricanes
21:38the Empire State Building will soon be tested by one of Mother Nature's most destructive forces
21:59new york's iconic Empire State Building towers over Manhattan
22:03just as it has for 90 years
22:07these 103 stories of glass, stone and steel face an invisible and unpredictable threat
22:16hurricane force winds
22:21research scientist Mark Oren tracks the wind speeds over Manhattan
22:25from the City College of New York's weather station
22:29so we're on top of a tall building about five miles from the Empire State Building in midtown Manhattan
22:38his research investigates the wind patterns flowing across the city
22:45Manhattan, perched by the Atlantic coast, is exposed to nature's worst
22:51there have been a number of hurricanes that have actually hit Manhattan
22:57and caused a lot of damage
23:03the top of the Empire State Building faces a battering ram of pressure from all directions
23:10to understand the threat it faces
23:12Mark analyzes measurements recorded over the last 10 years
23:18we've taken data from various weather stations
23:21that are located on the ground in the New York City metro area
23:25up here in Central Park
23:2889 miles per hour was the maximum 3 second wind gust
23:33down here in midtown Manhattan, 41 miles per hour
23:38but powerful gusts of wind are only part of the problem
23:42in midtown Manhattan
23:44the huge concentration of tall buildings disrupts wind
23:49avenues of skyscrapers act like vast wind tunnels
23:53funneling and amplifying the wind to dangerous speeds
23:57you have very tall buildings that creates a lot of turbulence
24:02and makes the wind very difficult to measure
24:06how does the Empire State Building stay upright in these phenomenal wind conditions
24:12the force of the wind pushing onto the facade can be immense
24:16but the rigid stone stays firm
24:20it channels the wind energy inside
24:22to the steel frame within
24:26at its heart is a backbone reinforced with diagonal steel cross braces
24:36they're encased in solid concrete
24:38that is not only strong but incredibly stiff
24:44together the steel and concrete form a rock solid core
24:48but can this 1930s technology stop the tower swaying violently
24:54in today's hurricane force winds
24:58Don Friedman examines how New York skyscrapers behave in extreme conditions
25:04there are actually buildings pretty much all over the place
25:08that are famous for being a little too limber in the wind
25:12a badly designed skyscraper will result in disastrous damage and collapse
25:17Don and his colleague Shaquana model the Empire State Building's inner steel skeleton
25:22okay so let's take a look at this model
25:25so we did a comparison of the moment frame of a building
25:29one is without any cross bracing
25:31as the wind speed increases
25:33the model building starts to move
25:36over here
25:38on this screen we have the cross bracing
25:41which you can see is a drastic difference in how the building behaves all together
25:46wind clearly affects the two frames in different ways
25:49what these simple models show is that the addition of cross bracing
25:53reduces the side sway under wind load to about an eighth of what it previously was
25:59and people notice when buildings move too much
26:04cross bracing gives stability to simple structures
26:07and super tall skyscrapers
26:10it reduces any sideways movement dramatically
26:13this simple but effective engineering solves a potentially catastrophic problem
26:18for the Empire State Building
26:20the old buildings were very well designed
26:22even with the more primitive tools
26:25with access to today's computer models
26:28the building's engineers might have found a very different solution
26:35as wind rushes around a skyscraper
26:38it creates swirling eddies
26:40that push the tower side to side
26:42making it sway dangerously
26:46so modern super tall skyscrapers are designed with ingenious profiles
26:52that disrupt the wind and stop the sway
26:57some buildings like the super skinny Park Avenue tower in New York
27:02have holes to simply let the wind pass through
27:08others have mass dampers inside
27:11huge traveling weights that counteract the swaying force and keep the building steady
27:19the Empire State Building is a textbook example of solid engineering
27:24built to withstand everything that nature can throw at it
27:27but in 1945 a totally unexpected force strikes it
27:33one engineers couldn't foresee
27:51on July 28th 1945 disaster strikes the Empire State Building
27:58a B-25 bomber with three crewmen on board
28:02is on a routine transport flight from an army base in Massachusetts
28:07it's flying over Manhattan headed for Newark Airport just across the city
28:12the weather is relatively bad the visibility is poor there's fog across Manhattan
28:17what happens next has no warning
28:22traveling at over 200 miles an hour
28:24the bomber flies straight at the Empire State Building
28:31it tears a 250 square foot hole in the 79th floor
28:37carving a path of destruction
28:40starting fires
28:41and snapping elevator cables
28:46one engine rips through the entire building
28:49and breaks through the opposite wall
28:54the other engine tumbles down an elevator shaft
28:57falling 1,000 feet to the sub-basement
29:01how does the Empire State Building survive this catastrophic accident
29:07engineer Adrian Brueger explores this engineering mystery
29:12the bomber pierces through the facade
29:15it's an immense impact like getting punched by a sledgehammer
29:22the B-25 Mitchell bomber is a formidable machine
29:27it weighs up to 35,000 pounds
29:31and flies at nearly 300 miles per hour
29:36it strikes the north wall with an immense amount of energy
29:41how is it that people inside the building survive this disaster?
29:46steel beams make up the skeleton of the Empire State Building
29:50Adrian wants to test what force of impact they can withstand
29:56what you see here is a beam like you would find in the floor joists
30:01or the floor beams of the Empire State Building
30:04and it would hold up the floors
30:06what we will see is how much ductility
30:09how much ability this steel has to actually deform before it breaks
30:13Adrian applies three tons of force to the steel beam
30:21so now we are pushing on the beam still and you can see that it's deflecting very heavily
30:30something moved a little
30:33we're okay, we can keep going
30:35as Adrian increases the weight load to 3.9 tons
30:39the steel beam is still holding strong
30:42as you can see this is absolutely amazing
30:45the beam is completely deformed in the middle
30:48but it's still holding almost 4 tons of spring energy
30:52it looks like it failed but it's actually still doing its work
30:56this steel has an incredible ductility
30:59it can bend in half before it snaps
31:03a photo of the impact the B-25 makes on the building
31:07proves the incredible strength of the beams
31:11here you can see these beams look very much like what we have here
31:16they're mangled, they're twisted, but they're not broken
31:19and that's important, they're not fractured
31:21so they stayed in place, and that's key
31:23the steel beams are bent, not broken
31:27the structure survives the main force of the initial impact
31:33many escape
31:35others are rescued by first responders
31:4014 people die in the tragic accident
31:46but there is a miraculous survival story
31:50astonishingly, the structure saves someone's life
31:5620 year old Betty Lou Oliver is an elevator operator
32:01she's blasted out of her elevator car on the 80th floor when the plane hits
32:08onlookers hurry her into another car to get her to safety
32:11but as the doors close, the cable snaps
32:15and the car instantly drops
32:18as Betty Lou's car picks up speed, the emergency brakes fail
32:24but trapped air compresses in the shaft, slowing her fall
32:29and at the bottom the severed cable forms a coil that cushions the impact
32:35miraculously, Betty Lou survives falling 1000 feet
32:41the Empire State Building survives the plane crash too
32:44but the moment of impact causes another potentially lethal risk to the structure and life inside
32:52the plane's fuel ignites disastrously
32:57these exclusive motion pictures show the Empire State Building burning like a great smoky torch
33:02with flames bursting from the window
33:07fire and skyscrapers can be a deadly combination
33:11but how does the building survive?
33:17Adrian wants to find out how the Empire State Building steel skeleton
33:21stands up to the flames and intense heat
33:23to save the people inside
33:25it's quite sharp
33:30what we were doing here is a good simulation of what you would expect to happen in
33:34for example, a hydrocarbon fire due to an airplane crash
33:39he heats the steel to find its breaking point
33:45go, go more
33:49there you go, that's it
33:51as the steel is heated
33:53a machine pulls from both ends with increasing force
33:57steel melts at 2500 degrees Fahrenheit
34:01but just a fraction of that temperature is enough to seriously weaken the metal
34:10there it is
34:14it's actually about 420 degrees Celsius
34:20the fire from the exploding bomber will quickly rage to double this temperature
34:26the integrity of the Empire State Building steel skeleton will easily fail with the heat of a fire
34:33it's vital the flames are put out before the skeleton fails and the building crashes
34:40fire does weaken the steel
34:42this is the Achilles heel of steel
34:47the Empire State Building's designers know that fire could bring an entire skyscraper down
34:54so they build in a hidden safety feature
34:58standpipes
34:59these rigid vertical pipes move water to the top of very tall buildings at great speed
35:06a standpipe acts like a fire hydrant at height
35:11it provides water to the firefighters who can hook up their hoses in the stairwell and fight the fires out
35:17on the floors
35:18fire safety officer Matt Pernal checks standpipes in New York's tallest skyscrapers
35:25the Empire State Building standpipe system consists of an impressive 7,340 feet of pipe and 6 miles of hose
35:37all right Jose we're set up down here I'm going to go ahead and get the churn test started
35:51we were able to reach the 500 gallons per minute the pump is putting out enough flow and pressure in
35:58order to reach the roof level and that will help the firefighters put out the fire
36:07in 1945 fire crews use the same standpipe system to quickly extinguish the blaze in the Empire State Building
36:17the flames are out within 40 minutes
36:20saving the metal from lethal structural damage
36:24and allowing it to reopen for business just two days after the crash with tens of thousands of people returning
36:31to work inside
36:34the Empire State Building's colossal structure can absorb the impact of a World War II bomber
36:40it can also survive hurricane force winds
36:45how does its gleaming facade stand up to the test of time?
37:03New York's Empire State Building is such an icon it's been called an eighth wonder of the world
37:09its gleaming facade is built from an extraordinary material
37:14at the time of construction many skyscrapers are coated in a layer of brick and ceramic terracotta
37:22the Empire State Building is covered in limestone
37:25the same stone as ancient wonders
37:28the 4500 year old Egyptian pyramids
37:34and the 2000 year old Roman Colosseum
37:38but what is the secret to its gleaming facade?
37:43geologist Polly Sturgeon traces the stone to its source to explore why architects choose it
37:50this is the Empire Quarry in Indiana
37:55in the 1920s they were pulling several hundred million tons of limestone out of this small stretch of land
38:02the limestone used to cover the Empire State Building's facade can only be found in this small area of the
38:08United States
38:09it's right in the heart of the Indiana stone belt this narrow 30 mile stretch of land
38:14which has produced up to 75% of all limestone buildings in North America
38:20the Indiana limestone is used in many of the country's most important buildings
38:25like the Pentagon
38:28and the Lincoln Memorial
38:30what makes it so sought after?
38:35Polly compares stone cores taken from test sites across the Indiana limestone belt
38:41so this is the Indiana limestone you can see it's a nice even color and texture
38:47layers of tiny crushed prehistoric sea creatures make up the limestone
38:52they give the rock its fine-grained structure
38:55there's no large shell sticking out or holes in it
38:58and that's because of the ocean environment that we had 340 million years ago here in Indiana
39:03waves would break all of those dead animal body parts into a nice even size
39:08makes it excellent for carving and putting on buildings
39:15workers can extract limestone from this quarry in 3-ton perfectly formed blocks without any faults
39:24gang saws then slice the stone into smaller pieces
39:29other popular building stones like granite or marble
39:32you can have areas of irregularity with those veins that make it difficult to carve large pieces
39:38the limestone can be cut and carved in any direction without cracking
39:45it's ideal for cutting the identical decorative details that are seen in the facade of the Empire State Building
39:53its faultless fine-grained structure appears to be the perfect building material
40:00but limestone has one potentially serious flaw
40:04it dissolves in rainwater
40:07limestone can weather away and be dissolved
40:11chemically all of our rainwater is slightly acidic so it does eat away at the rock
40:16poly uses diluted hydrochloric acid to demonstrate the effect it has on the stone
40:23you can put it on there and you can see that it fizzes very rapidly
40:27and because the Indiana limestone is so high in calcite it always reacts very vividly like this
40:38New York's acidic rainwater is slowly eating away at the facade of the Empire State Building
40:44but the Indiana limestone is so durable
40:47that it takes a staggering 60 years before any work is needed to repair or replace the stone covering the
40:54skyscraper
40:57meticulous cleaning and renovation ensures the limestone layer will never dissolve or crumble
41:04meaning this modern wonder can survive as long as the ancient wonders of the world
41:11the Empire State Building is an incredible achievement
41:16it's the first structure to top 100 stories
41:21the pioneering icon paving the way to ever taller skyscrapers
41:27it's extremely resilient
41:29with innovative engineering and far-sided use of materials
41:35this incredible building will stand firm in Manhattan's skyline for centuries to come
41:41the power of the whole world
42:05episode 3
42:11You
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