Original subtitles

Narrator: THE GREAT WALL OF CHINA.

THE LONGEST, MOST EXPENSIVE FORTIFICATION EVER BUILT.

Man: NO MATTER WHAT HEIGHT YOU CLIMB,

HOW GOOD YOUR EYES ARE,

NO MATTER HOW GOOD YOUR BINOCULARS ARE,

YOU CAN'T SEE IT ALL.

IT REALLY IS A GEOGRAPHICAL WONDER.

Narrator: IT'S RECOGNIZED ALL OVER THE WORLD,

BUT ITS CONSTRUCTION IS STILL SHROUDED IN MYSTERY.

EVERY TIME I COME TO A PLACE LIKE THIS ON THE GREAT WALL

WHERE IT STRETCHES FOR MILES AND MILES,

I'M JUST BLOWN AWAY EVERY SINGLE TIME.

Narrator: WHAT DID IT TAKE TO BUILD IT?

WHO WAS IT BUILT TO KEEP OUT?

ALTHOUGH THEY WERE FEW IN NUMBER,

THEY WERE THE MOST FEARED WARRIORS IN THE WORLD.

Narrator: THE ONLY WAY TO FIND OUT IS TO BLOW THIS WALL APART.

DISMANTLING ITS DEFENSES,

AND PULLING APART ITS TOWERS BRICK

BY BRICK WILL HELP US

UNEARTH THE ASTONISHING ENGINEERING SECRETS

AT THE HEART OF THIS ANCIENT WONDER.

-- Captions by VITAC -- www.vitac.com

CAPTIONS PAID FOR BY DISCOVERY COMMUNICATIONS

THE GREAT WALL OF CHINA.

A VAST FORTIFICATION THAT, IN TOTAL,

STRETCHES OVER 13,000 MILES ACROSS THE CONTINENT.

THIS IMMENSE MEGA-STRUCTURE WAS A DEFENSIVE SHIELD

FOR THE WORLD'S MOST POPULOUS NATION.

IT STRETCHES FROM SNOW-COVERED

DESERTS ALL THE WAY TO THE YELLOW SEA

AND WAS THE LARGEST CONSTRUCTION PROJECT

THE WORLD HAD EVER SEEN.

THIS WALL IS THE GREATEST MAN- MADE STRUCTURE ON OUR PLANET.

OVER A BILLION TOUGH CLAY BRICKS HELPED IT

SURVIVE FOR CENTURIES.

THE WALL RISES ABOUT 23 FEET HIGH

WITH TALL BATTLEMENTS TO SHIELD DEFENDERS...

AND BUILT-IN ARROW LOOPS FOR SHOOTING AT INVADERS.

THIS MONUMENTAL BRICK STRUCTURE IS THOUSANDS OF MILES

LONG AND STRETCHES OVER 16 FEET WIDE...

...WITH TENS OF THOUSANDS OF WATCH TOWERS STANDING GUARD.

FOR CENTURIES, IT WAS CHINA'S FIRST LINE OF DEFENSE,

BUT THE CONSTRUCTION OF THIS ICONIC

BRICK WALL WASN'T THE FIRST TIME THAT CHINA'S EMPERORS

HAD BUILT A BARRICADE ACROSS THE COUNTRY.

[ MAN VOCALIZING SPIRITUALLY ]

THEIR PREDECESSORS ERECTED PRIMITIVE EARTH WALLS

OVER 1,500 YEARS BEFORE THE FAMOUS

BRICK WALL WAS EVEN STARTED.

THE BIG MYSTERY -- WHAT DROVE CHINA'S RULERS

TO BUILD SUCH MAMMOTH STRUCTURES?

QUITE BEAUTIFUL MOUNTAINS, THESE,

AND MAKING THE SCENERY MORE MAGNIFICENT

IS THE WALL RIGHT HERE.

THIS WAS THE ANCIENT FRONTIER.

Narrator: WILLIAM LINDESAY IS ONE OF THE WORLD'S

FOREMOST GREAT WALL EXPERTS.

HE HAS WALKED THE WALL'S LENGTH

TO INVESTIGATE ITS MANY SECRETS.

THE THOUSANDS OF GREAT WALL MILES

UNDER WILLIAM'S BELT

HAVE GIVEN HIM A UNIQUE UNDERSTANDING

OF ITS HISTORY.

THIS WAY IS CHINA.

THIS WAY IS MONGOLIA, THE NOMADIC LANDS.

THE CHINESE HAD A GOOD DEAL. THEY COULD FARM.

THEY COULD PRODUCE A LOT OF FOOD,

MORE THAN THEY NEEDED.

PEOPLE IN THE NORTH, BAD DEAL.

IT'S IMPOSSIBLE TO FARM THERE.

THE GROWING SEASON IS TOO SHORT.

Narrator: THE NOMADS LIVED TO THE NORTH OF CHINA

AND MOVED THEIR HERDS WITH THE SEASONS.

THEY RAIDED CHINA ON HORSEBACK TO GET A HOLD OF THE GOODS

AND FOODS THEY COULDN'T PRODUCE THEMSELVES.

Lindesay: THE DROUGHT OR A TERRIBLE WINTER

COULD DESTROY EVERYTHING THE PEOPLE HAD,

AND THEN THEY HAD A SURVIVAL CHALLENGE.

WHERE TO GO FOR RELIEF.

THEY DIDN'T GO NORTH TO SIBERIA.

THEY NATURALLY CAME SOUTH AND TRESPASSED ON CHINESE LAND.

THE NOMADS WERE NATURALLY A CRACK ARMY.

FROM CHILDHOOD, THEY'RE RIDING HORSES --

EVEN WITHOUT SADDLES AND STIRRUPS.

THIS KIND OF SCHOOLING MADE THE NOMADS

THE MOST FEARED ARMY IN THE WORLD.

Narrator: TO MAKE THINGS WORSE FOR THE CHINESE,

THE NOMADS WEREN'T JUST EXCELLENT HORSEMEN.

THEY ARMED THEMSELVES WITH AN INCREDIBLY

SOPHISTICATED WEAPON --

THE COMPOSITE BOW.

YANG FUXI IS ONE OF THE WORLD'S BEST BOWMAKERS.

FOR TEN GENERATIONS, HIS FAMILY HAS PRACTICED THIS ANCIENT,

NOBLE ART, WHICH WAS THE KEY

TO MAKING THE NOMAD HORDE SO DEVASTATING.

MASTER YUNG'S TASK IS TO CREATE A BOW

THAT STORES ENOUGH ENERGY TO KILL A MAN.

HIS FIRST STEP IS TO CARVE OUT AND GLUE

TOGETHER THE BOW'S WOODEN CORE.

BUT WOOD ON ITS OWN DOESN'T HAVE THE FLEX

AND STRENGTH TO PROPEL AN ARROW TO A LETHAL SPEED.

THE SECRET THAT STOPS THE WOODEN BOW

FROM SNAPPING IS ITS CLEVER CONSTRUCTION.

MASTER YUNG GLUES A LAYER OF TOUGH

BUFFALO HORN ONTO THE BOW

TO MAKE THE WOODEN CORE STRONGER.

TO GIVE THE BOW A BIGGER PUNCH,

HE GLUES TENDONS FROM A BULL'S NECK ONTO THE OTHER SIDE.

UPON RELEASE, THE ARROW FLIES AWAY

AT AN ASTOUNDING 186 MILES PER HOUR.

HOW COULD THE CHINESE DEFEND THOUSANDS OF MILES OF TERRITORY

AGAINST THESE VICIOUS NOMAD ATTACKS?

[ BIRDS CHIRPING ]

Narrator: IN ORDER TO PROTECT THE ANCIENT CHINESE

FROM INVADING MONGOLIANS,

AN ELABORATE BARRIER THOUSANDS OF MILES

LONG WAS CONSTRUCTED.

BENEATH THE BRICK WE SEE TODAY

LIE THE REMAINS OF AN EARLIER EARTHEN WALL.

LAYERS OF COMPACTED SOIL CREATED A ROCK-HARD BARRICADE.

THIN REED MATS SEPARATED THE LAYERS

FOR STABILITY AND DRAINAGE.

THESE MULTI-LAYERED EARTH WALLS ROSE UP NEARLY 20 FEET TALL.

SATELLITE IMAGERY REVEALS THAT THESE FIRST WALLS

STRETCHED FROM THE YELLOW SEA

ALL THE WAY TO THE DESERT OF WESTERN CHINA.

BUT HOW DID THE CHINESE BUILD A WALL LIKE THIS

IN A BARREN DESERT

WITH NO OBVIOUS BUILDING MATERIALS AROUND?

Fairbrother: EVERY TIME I COME TO A PLACE LIKE THIS ON THE GREAT WALL

WHERE IT STRETCHES FOR MILES AND MILES,

I'M JUST BLOWN AWAY EVERY SINGLE TIME.

Narrator: GREAT WALL EXPLORER RICHARD FAIRBROTHER

IS IN CHINA'S WESTERN DESERT.

HE'S SEARCHING FOR SECRETS OF THE EARLIEST GREAT WALL,

WHICH WASN'T MADE OF BRICKS, BUT OUT OF SOIL.

IT'S AMAZING TO THINK ABOUT THE NUMBER OF PEOPLE

INVOLVED AND THE AMOUNT OF LABOR

IT TOOK TO BUILD SOMETHING LIKE THIS.

Narrator: TO INVESTIGATE HOW THE WALLS

HAVE STOOD UP TO THESE HARSH DESERT WINDS...

...RICHARD IS GOING TO RECONSTRUCT PART OF THE WALL.

BUILDER MR. YUNG AND HIS TEAM

ARE USING ORIGINAL METHODS FOR THIS PROJECT.

THE FINISHED STRUCTURE IS KNOWN AS A RAMMED EARTH WALL.

YOU BUILD THESE WALLS BY LAYERS OF SOIL,

AND THEN LAYERS OF THESE REEDS,

AND YOU PUT THEM ON TOP THERE,

AND THEN SPREAD THEM AROUND.

ONE ANOTHER ADVANTAGE OF THESE REEDS

IS THAT THEY PROVIDE A DRAINAGE MECHANISM FOR THE WALL.

SO THE RAIN COMES DOWN THROUGH THE SOIL,

AND THEN IS PASSED OUT BY THE STRUCTURE OF THESE REEDS.

Narrator: EVEN WITH REEDS FOR DRAINAGE, VIOLENT STORMS

AND SCOURING WINDS EVENTUALLY WEAR EVERYTHING

TO DUST IN THIS UNFORGIVING LANDSCAPE.

SO, HOW ARE PARTS OF THE WALL

OVER 2,000 YEARS OLD STILL STANDING?

LAB TESTS REVEAL THAT THE DESERT SOIL KNOWN AS "LESS"

HAS A SPECIAL PROPERTY THANKS IN PART

TO THE CRUSHED SHELLS OF LONG-DEAD SNAILS.

LESS IS RICH IN CALCIUM CARBONATE,

AND WHEN THAT'S EXPOSED TO WATER,

IT GIVES THE WALL OR THE SOIL A SELF-CEMENTING CHARACTERISTIC.

Narrator: THE ANCIENT BUILDERS

UNKNOWINGLY MADE USE OF THIS CLEVER CHEMISTRY

TO BUILD A WALL THAT STOOD FOR MILLENNIA.

THE PURPOSE OF THE RAMMING

IS TO COMPRESS THE LAYERS TOGETHER AND...

...GIVE IT THAT TREMENDOUS STRENGTH

THAT THESE RAMMED-EARTH WALLS ARE KNOWN FOR.

IF YOU HAVE TO DO IT ALL DAY LONG IN THE BLAZING DESERT SUN,

I THINK YOU'D BE PRETTY KNACKERED BY THE END.

Narrator: A TEAM OF 80 MEN COULD BUILD OVER A HALF-MILE OF WALL

IN JUST 7 DAYS.

IT TOWERED ALMOST 20 FEET TALL

AND KEPT ENEMIES OUT OF CHINA FOR CENTURIES.

AND THE ONLY WAY THROUGH WAS TO CLIMB

THE WALL UNDER A HAIL OF LETHAL ARROWS.

BY THE 16th CENTURY, THINGS HAD CHANGED.

CHINA'S ENEMIES HAD MORE FEROCIOUS WEAPONS.

AND THE OLD WALLS WERE LACKING.

THEY ALREADY HAD A LOT OF WALL, SO WHAT WAS THE NEXT OPTION?

MORE WALL? BETTER WALL?

THAT WAS THE QUESTION TO BE ANSWERED.

Narrator: THE ONLY OPTION WAS TO UNDERGO

THE MOST AMBITIOUS CONSTRUCTION PROJECT

THE WORLD HAD EVER SEEN.

Narrator: THE ORIGINAL GREAT WALL OF CHINA

WAS BUILT FROM MUD OVER 2,000 YEARS AGO...

AND CONSTRUCTED TO DEFEND THE CHINESE EMPIRE

AGAINST NOMAD ATTACK.

BUT OVER THE CENTURIES, AS WARFARE DEVELOPED,

THIS EARTH WALL BECAME A LESS FEARSOME OBSTACLE.

MILITARY ADVANCED FORCED THE CHINESE

TO STRENGTHEN THEIR LINE OF DEFENSE.

HISTORIAN WILLIAM LINDESAY IS WALKING THE GREAT WALL

AT JIANKOU IN THE MOUNTAINS NORTH OF BEIJING.

HE'S TRYING TO UNDERSTAND WHAT PROMPTED THE CHINESE

TO UPGRADE THIS VAST DEFENSIVE BARRIER.

JUST 50 MILES OVER THERE IS BEIJING.

THAT WAS NOT A VERY SAFE POSITION.

IN 1550, THE MONGOLS STORMED THROUGH THE WALL.

[ SWORDS CLASHING ]

AND THE VULNERABILITY OF BEIJING'S POSITION

CAME INTO PERSPECTIVE.

Narrator: THE MONGOLIAN NOMADS SURGED THROUGH THESE MOUNTAINS

TO THE LAND SURROUNDING THE CHINESE CAPITAL, BEIJING.

THEY DEVASTATED THE CIVILIAN POPULATION,

AND THE CHINESE RULING DYNASTY FACED A HUGE DILEMMA.

Lindesay: THE COURT AND THE CORRIDORS

OF POWER WERE ABSOLUTELY SHAKING IN FEAR.

THE QUESTION WAS, HOW COULD THE GREAT WALL OF CHINA FAIL?

Narrator: THE TIME HAD COME FOR A NEW AND IMPROVED WALL.

THE CHINESE BUILT A VAST STRUCTURE

USING BILLIONS OF TONS OF SOLID STONE AND BRICKS.

IT SAT ON A STURDY FOUNDATION OF HUGE GRANITE BLOCKS.

SMOOTH BRICKS MADE THE SHEER WALLS

ALMOST IMPOSSIBLE TO SCALE.

EMBATTLEMENTS PROTECTED THE DEFENDERS AT THE TOP.

RUBBLE WAS CRAMMED BETWEEN THE BRICK FACES

TO CREATE A STABLE CORE.

AND SMOOTH STONES PAVED THE TOP.

NEARLY 23 FEET HIGH AND OVER 16 FEET THICK,

THIS WALL WAS IMPENETRABLE.

SO, HOW DID THE BUILDERS PRODUCE ENOUGH BRICKS

TO BUILD A WALL ACROSS CHINA?

COLIN RICHARDS HAS THE ANSWER.

HE HAS SPENT HIS CAREER CONSERVING BRICK BUILDINGS.

TODAY, HE JOINS AN EXTRAORDINARY $15 MILLION PROJECT

TO RESTORE THIS MAGNIFICENT STRUCTURE.

ALONGSIDE AN EIGHT-MAN RESTORATION CREW,

HE'S USING ORIGINAL CONSTRUCTION TECHNIQUES TO INVESTIGATE

JUST HOW DIFFICULT IT WAS TO BUILD THE GREAT WALL.

ANY EXCESS, THROW IT INTO THE MOLD.

NOW WE JUST NEED TO MAKE SURE IT GETS TO THE CORNERS.

IF WE CAN GET THIS OFF EASY, THEN WE'VE GOT A GOOD BRICK.

Narrator: THE SECRET TO BUILDING A WALL QUICKLY

IS TO USE BIG BRICKS MADE OF CLAY.

THE BRICKS ON THE GREAT WALL ARE FOUR TIMES LARGER

THAN THE BRICKS WE USE TODAY TO BUILD HOUSES.

THE BIGGER YOU CAN CREATE THEM,

ALTHOUGH THEY'RE VERY HEAVY TO MOVE,

THEN THE QUICKER YOU CAN BUILD THE WALL,

BECAUSE YOU'RE SIMPLY STACKING ONE ON TOP OF EACH OTHER.

I'M HAPPY WITH THAT.

WE CAN SMOOTH OUT THE SIDE.

THAT CAN DRY OUT.

IT'LL GO IN THE KILN,

AND WE'LL HAVE ANOTHER BRICK FOR THE GREAT WALL OF CHINA.

Narrator: THE TEAM LEAVES THE BRICKS TO DRY.

NOW THEY NEED FIRING.

Richards: WE'RE PUTTING THE LAST FEW BRICKS

ONTO THE TOP OF THE KILN,

AND WE'VE LEFT SPACES BETWEEN THEM SO THAT

THE HEAT CAN COME UP TO THE TOP OF THE KILN,

STAY THERE BEFORE IT MAKES ITS JOURNEY BACK DOWN AGAIN

AND OUT THROUGH THE CHIMNEYS.

AND WE'LL PUT A BIG LAYER OF EARTH ONTO THE TOP,

WHICH WILL INSULATE,

KEEP THE HEAT IN FOR AS LONG AS WE CAN.

Narrator: IT TAKES COLIN AND THE TEAM A MORNING OF HARD,

PHYSICAL LABOR JUST TO LOAD THE KILN.

FIRING WILL FUSE THE CLAY PARTICLES IN THE BRICKS

TO MAKE THEM EXTREMELY TOUGH.

WHEN THE WALL WAS FIRST BUILT,

THOUSANDS OF KILNS LIT UP THIS LANDSCAPE.

TO PRODUCE PERFECTLY FIRED BRICKS,

COLIN AND THE TEAM RELY ON THEIR YEARS OF EXPERIENCE

TO CAREFULLY CONTROL THE KILN'S TEMPERATURE.

Richards: WE HAVE TO KEEP AN EYE ON THE COLORS

THAT THE BRICKS ARE GOING TO.

WE GO THROUGH A SORT OF RED HOT,

A YELLOW HOT, A WHITE HOT.

AND ONCE WE'RE ON THE WHITE HOT,

WE HAVE TO HOLD IT AT THAT FOR 12 HOURS

TO ENSURE THAT TEMPERATURE,

WHICH IS AROUND 1,000 DEGREES,

SPREADS THROUGH THE STACKS OF BRICKS,

AND THEN STOP THE FIRING.

Narrator: THE BRICK KILN WORKS THROUGH AN INGENIOUS DESIGN.

THE FIRE ISN'T UNDER THE BRICKS,

BUT BESIDE THEM IN A TUNNEL THAT DRAWS IN FRESH AIR.

THE KILN'S SHAPE FORCES HOT AIR DOWN THROUGH THE BRICKS

AND OUT OF THE THREE CHIMNEYS SO THE BRICKS FIRE EVENLY.

YEAH. 24 HOURS AFTER THE SUCCESSFUL FIRING,

THE CREW MUST HAUL THESE NEWLY FIRED BRICKS UP TO THE WALL.

SO HOW DID THE WALL'S ORIGINAL BUILDERS

MOVE BILLIONS OF BRICKS

FROM THE KILNS TO THE TOP OF HIGH MOUNTAIN PEAKS?

Richards: THE TRANSPORTATION OF THESE SORT OF HEAVY OBJECTS

FROM ONE PLACE TO ANOTHER, YOU KNOW, IS VERY ARDUOUS.

Narrator: JUST LIKE THEIR ANCIENT COUNTERPARTS,

COLIN AND THE TEAM HAVE ONLY ONE OPTION

TO GET THE WORK DONE -- MANPOWER.

Richards: WE NEED ALL THE LABOR WE CAN GET

BECAUSE THE MORE PEOPLE YOU'VE GOT,

THEN THE EASIER THE TASK BECOMES.

Narrator: MORE THAN 1 MILLION MEN

WERE PUT TO WORK BUILDING THE WALL,

CONSTANTLY FIRING, TRANSPORTING,

AND LAYING NEW BRICKS.

TODAY, INVESTIGATORS LIKE WILLIAM ARE TRYING

TO SOLVE ANOTHER OF THE GREAT WALL'S ENDURING MYSTERIES.

HOW DID THE ARCHITECTS DETERMINE THE BEST PATH AGAINST INVADERS?

WHENEVER VISITORS REACH THE WALL,

THEY ALWAYS TEND TO ASK THE SAME QUESTIONS.

AND ONE OF THOSE QUESTIONS IS, WHY IS THE WALL HERE

AND NOT OVER THERE OR OVER HERE?

Narrator: WILLIAM STUDIES THE LANDSCAPE AROUND

THE GREAT WALL TO UNDERSTAND

WHY THE CHINESE BUILT WHERE THEY DID.

Lindesay: FROM THE TOP OF THIS WATCH TOWER,

I CAN SEE PRECISELY WHY THE WALL IS HERE.

DOWN HERE, LOW GROUND, ASCENDING, ASCENDING,

AND THIS IS THE PEAK.

AND THE WALL IS TAKING THAT PEAK LINE

TO THE PEAK OVER THERE.

I MOVE TO THE RIGHT, AND THE WALL DESCENDS.

LEVEL OF THE MOUNTAINS FALLS AWAY DRAMATICALLY.

THIS IS THE ABSOLUTELY PERFECT LINE

FOR THIS SECTION OF WALL.

Narrator: THE WALL'S BUILDERS FOLLOWED THE HIGH GROUND,

BUT THEIR PATH WAS NEVER A SIMPLE, STRAIGHT LINE.

Lindesay: INITIALLY, I COULDN'T SEE ANY LOGIC

IN THAT SEEMINGLY HAPHAZARD ROUTE THAT THE WALL TOOK.

BUT ACTUALLY, ALL OF THESE TWISTS

AND TURNS, I BELIEVE, ARE FOR A PURPOSE.

IT IMPROVED THEIR OPPORTUNITIES IN TERMS OF LINES OF FIRE.

NOT ONLY IN THE FACES OF THE ENEMY,

BUT FROM THE SIDE.

NO ENEMY IN THEIR RIGHT MIND

WOULD WANT TO FIGHT WITH THE CHINESE RIGHT HERE.

Narrator: THE CHINESE BUILT THE GREAT WALL TO FOLLOW THE TERRAIN,

RISING 4,921 FEET TO THE TOPS OF MOUNTAINS.

THEY POSITIONED WATCH TOWERS 492 FEET APART

TO MAXIMIZE THEIR KILL ZONES.

AND CLEARED THE TREES FOR TWO MILES

SO RAIDERS WERE IN CLEAR VIEW.

SPURS EXTENDED THE LINE OF SIGHT TO GUARD AGAINST ATTACKS.

THE WALL WAS A HUGE PHYSICAL BARRIER.

BUT WITHOUT SOLDIERS, IT WASN'T STOPPING ANYBODY.

HAD THE CHINESE JUST BUILT A WALL IN THE HOPE

THAT THAT WOULD KEEP THE NOMADS ON THEIR HORSES OUT,

THAT WOULD HAVE BEEN COMPLETELY USELESS.

THE WALL HAD TO BE PERMANENTLY GARRISONED,

ACTIVELY MANNED.

Narrator: JUST HOW MANY WARRIORS

WOULD IT TAKE TO PATROL THIS MASSIVE WALL?

AND WHERE WERE THEY ALL GOING TO LIVE?

Narrator: THE CHINESE CONSTRUCTED HUGE SECTIONS OF THE 16th CENTURY

GREAT WALL FROM BRICKS AND MORTAR.

IT PRESENTED A FORMIDABLE BARRIER

TO CHINA'S ENEMIES.

BUT WITH NO ARMY TO REPEL THESE ATTACKERS,

THE WALL ALONE WAS NOT ENOUGH.

THE PERFORMANCE OF THE WALL DEPENDED ON WHO WAS MANNING IT,

HOW MANY MEN THERE WERE.

Narrator: WILLIAM LINDESAY IS AT JINSHANGLING,

NORTH OF BEIJING, TO INVESTIGATE

HOW THE CHINESE MANNED THIS WALL

WITH A MILLION SOLDIERS.

Lindesay: I BELIEVE THIS IS THE PROTOTYPE SECTION

FOR THE REDESIGN OF THE WALL.

NOWHERE ELSE DO YOU FIND THE TOWERS SO CLOSE TOGETHER.

Narrator: THE CHINESE BUILT THE BRICK WALL

WITH THESE TOWERS JUST 492 FEET APART.

Lindesay: TOWERS LIKE THESE PROBABLY ACCOMMODATED 20 TO 30 MEN.

I FOUND FIGURES EARLY 1600s

OF 120 PER KILOMETER.

PRETTY INTENSE GARRISON LEVELS.

Narrator: LIVING HUNDREDS OF MILES FROM CIVILIZATION,

HOW DID THESE SOLDIERS SURVIVE IN NEAR ISOLATION?

THE ANSWER LIES INSIDE THE WALL.

TENS OF THOUSANDS OF TOWERS HOUSED THE TROOPS.

EACH TOWER'S FIRST FLOOR SLEPT UP

TO 30 SOLDIERS ON STONE BEDS,

WHILE COAL FIRES KEPT THE ROOMS WARM

DURING FREEZING WINTERS.

WALLS 36 FEET HIGH AND OVER

3 FEET THICK PROTECTED THE SOLDIERS,

AND WINDOWS ALLOWED FOR A CONSTANT LOOKOUT.

ON THE UPPER LEVEL, A WEAPONS STORE KEPT THE SOLDIERS ARMED

WHEN THEY FACED AN ATTACK.

THESE TOWERS GARRISONED THE ARMIES

THAT STOOD GUARD ON THE WALL ALL YEAR ROUND.

THE GREAT WALL AND ITS THOUSANDS OF TOWERS CONTAIN

MORE BRICKS THAN ANY OTHER BUILDING ON THE PLANET.

RESTORATION EXPERT COLIN RICHARDS

IS HELPING A CREW REBUILD A DERELICT SECTION OF WALL.

THE CREW HAS MADE NEW BRICKS.

NOW THEY MUST FIX THEM TOGETHER WITH MORTAR.

THIS MORTAR CAN BE INCREDIBLY HARD, AND IN SOME INSTANCES,

HARDER THAN THE BRICKS THEMSELVES.

AND I'VE GOT A PICTURE HERE WHICH SHOWS THE MORTAR

STANDING PROUD OF THE BRICKS.

Narrator: IN SECTIONS, THE GREAT WALL'S BRICKS HAVE ERODED AWAY,

LEAVING A LATTICE OF THE STRONGER MORTAR BEHIND.

Richards: THEY'VE ERODED BEYOND THE FACE OF THE WALL,

AND IT JUST DEMONSTRATES

WHAT AN INCREDIBLE MATERIAL THIS IS.

Narrator: THE MIX OF THE MORTAR REMAINS A MYSTERY.

THERE'S NO WRITTEN RECORD OF THE ORIGINAL RECIPE.

BUT COLIN'S HEARD FROM THE LOCAL FARMERS

THAT THE KEY TO ITS STRENGTH LAY IN A SURPRISING INGREDIENT --

RICE.

TO INVESTIGATE, COLIN USES A CRUDE TECHNIQUE

TO ANALYZE THE MORTAR'S CONTENTS.

IF YOU TAKE A LUMP OF THE ORIGINAL MORTAR

AND BREAK IT DOWN AS FINELY AS YOU CAN

AND THEN ADD IT TO WATER, AGITATE THE MIX,

THEN YOU SHOULD GET VARIOUS SETTLEMENT OF DIFFERENT LAYERS,

AND THAT WILL ALLOW YOU TO IDENTIFY

WHAT THE MIX WAS CONSTRUCTED OF.

Narrator: HE LEAVES THE CRUSHED MORTAR TO SETTLE FOR THREE HOURS,

AND THEN CHECKS IT.

WHAT IS SURPRISING IS THAT WE CAN SEE THAT THERE IS

QUITE A LOT OF AGGREGATE IN THE MORTAR.

YOU KNOW, THERE'S SAND.

THERE'S SORT OF CRUSHED STONE, THERE'S SILT.

SO THERE WAS A LOT OF SORT OF BINDING MATERIAL IN THE MORTAR,

AND THAT IS REALLY INTERESTING BECAUSE IT'S A VERY STRONG MIX.

Narrator: THE AGGREGATE IN THE MIX

MAKES THE MORTAR PACK TOGETHER TIGHTLY,

BUT COLIN TRUSTS WHAT LOCALS SAID

ABOUT THE STICKY RICE WATER.

Richards: IN THIS PART OF CHINA, RICE WAS IN ABUNDANCE,

AND THEY FOUND THAT IF THEY ADDED IT TO THE MORTAR,

NOT ONLY WOULD IT SET MORE QUICKLY,

BUT IT WAS FAR MORE DURABLE.

Narrator: COLIN IS MAKING A BATCH OF STICKY RICE

MORTAR FOR HIS OWN BRICKS.

Richards: WE NEED TO BOIL THIS WATER

AND GET IT SORT OF BUBBLING QUITE QUICKLY,

AND THEN ADD OUR RICE TO IT.

Narrator: SCIENTISTS BELIEVE THAT THE STARCH IN THE RICE

GAVE THE MORTAR ITS EXTRA STRENGTH.

COLIN MIXES HIS FRESH MORTAR USING LIME, SAND,

AND HIS SPECIALLY PREPARED STICKY RICE WATER.

Richards: WHAT WE HAVE TO DO IS TRY TO LAY A BED OF MORTAR

SO THAT THE MORTAR SPREADS TO THE EDGES.

IF IT'S TOO THICK, IT WON'T DO THAT.

IF IT'S TOO WET, IT JUST SPILLS OVER THE SIDES.

SO GETTING IT ABSOLUTELY RIGHT IS CRITICAL

TO THE QUALITY OF THE MORTAR.

Narrator: WORKING LIKE THIS,

THE WALL BUILDERS COULD STACK BRICKS HIGH

AND BUILD THE THOUSANDS OF TALL TOWERS

NEEDED TO SHELTER THE GREAT WALL'S

VAST STANDING ARMY.

THESE FIGHTING MEN, FAR AWAY FROM CIVILIZATION,

STOOD ALONE AGAINST NOMAD ATTACK.

WILLIAM LINDESAY IS EXPLORING

HOW THE WALL'S ARCHITECTURE KEPT THE MEN SAFE,

EVEN WHEN THE NOMADS INVADED.

JUST IMAGINE, YOU'RE A CHINESE DEFENDER.

HERE YOU STAND.

AS AN ATTACKER, I DON'T STAND A CHANCE.

THE DEFENDER IS SIX FEET ABOVE ME.

SWITCH POSITION.

GOT THE HEIGHT ADVANTAGE.

LEFT HAND THE SHIELD,

HERE, THE SWORD, A SPEAR, A CUDGEL.

THIS IS REALLY A BRILLIANT ACCESSORY FORTIFICATION.

Narrator: BUT HAND-TO-HAND COMBAT WASN'T THE ONLY FORM OF DEFENSE.

CHINESE TECHNOLOGICAL PROWESS PROVIDED THE SOLDIERS

WITH A FORMIDABLE ARSENAL OF WEAPONS.

THIS TERRACE IS ACTUALLY A CANNON PLATFORM.

OF COURSE, THE CANNON'S GONE,

BUT THE BARREL WOULD BE HERE.

YOU MIGHT THINK THIS BIG BOOMER

IS THE MOST DEVASTATING WEAPON ON THE WALL.

ACTUALLY, IT CREATES A LOT OF NOISE.

IT HAS THE FEAR FACTOR,

BUT IT TAKES SO LONG TO RELOAD.

SO SLOW AND SO FINICKY IN THE WINDY, WET WEATHER.

IT'S ACTUALLY NOT THE MOST RELIABLE WEAPON.

Narrator: FOR SOMETHING MORE VERSATILE THAN THE CANNON,

THE SOLDIERS ON THE WALL EMPLOYED A FAR MORE ACCURATE

AND DEADLY TOOL...

...THE CROSSBOW.

[ BOW CREAKING ]

THIS FEROCIOUS WEAPON WAS MORE THAN A MATCH

FOR THE NOMAD'S COMPOSITE BOWS,

AND IT WAS THE WEAPON OF CHOICE FOR THE CHINESE SOLDIERS

MANNING THE WALL.

YANG FUXI HAS A COPY

OF THE CROSSBOW'S TRIGGER MECHANISM,

A WONDER OF ITS AGE.

THE CROSSBOW TRIGGER WAS THE WORLD'S FIRST MECHANICAL WEAPON.

IT RELEASED THE BOLT IN A SPLIT SECOND TO FIRE

WITH INCREDIBLE ACCURACY.

SOLDIERS OFTEN DIPPED BOLTS IN POISON

TO MAKE SURE THAT EVEN A SCRATCH WAS FATAL.

[ MAN SCREAMS ]

THE WATCH TOWERS PROTRUDED FROM THE WALL.

THIS WAY, ITS DEFENDERS COULD CATCH ATTACKERS

IN A DEADLY CROSSFIRE.

[ MEN SHOUTING ]

BEHIND THE WALL BATTLEMENTS, SOLDIERS DROPPED STONE BOMBS

AND FIRED CANNONS.

[ EXPLOSIONS ]

BUT THE CROSSBOW WAS STILL THE WEAPON OF CHOICE.

THE CHINESE CREATED AN INDUSTRIAL PRODUCTION LINE

TO CAST CROSSBOW TRIGGERS BY THE THOUSANDS.

ITS INCREDIBLE DESIGN MEANT THAT THE CHINESE

COULD DEPLOY A VAST ARMY OF SOLDIERS

WHO COULD OPERATE THE CROSSBOW

WITHOUT EITHER SKILL OR STRENGTH.

BUT WEAPONS ALONE COULDN'T DETER THE RAIDERS.

CLANDESTINE MEASURES WOULD BE NECESSARY.

Narrator: THE GREAT WALL OF CHINA WAS

STRATEGICALLY DESIGNED FOR SOLDIERS

AND THEIR WEAPONS OF WAR.

THIS HOLE WAS FOR ANCHORING THE CROSSBOW.

A STANDARD BOW MOUNTED

ON A STOCK, UNDERNEATH IS A KNOB.

IT GOES IN THERE, AND IT ALLOWS THE USER

TO QUICKLY LEAVE A BACK RELOAD,

WAIT UNTIL HE SEES HIS TARGET, AND FIRE.

Narrator: BUT THE MIGHTY CROSSBOW

COULD ONLY PROTECT THE WARRIORS FOR SO LONG.

ISOLATED IN SMALL WATCH TOWERS HIGH IN THE MOUNTAINS

AND DEEP IN THE DESERTS...

...THE SOLDIERS WERE SOMETIMES

IN NEED OF SUPPORT FROM THEIR COMRADES.

SO, IMAGINE BEING A CHINESE SOLDIER

STATIONED ON THE WALL.

SUDDENLY OVER THE HORIZON COMES 300,

400 HORSEMEN WITH DUST TRAILING BEHIND THEM.

YOU HAVE TO WONDER WHAT ON EARTH THEY WOULD DO

WHEN THEY SAW SOMETHING LIKE THAT.

Narrator: GREAT WALL EXPLORER RICHARD FAIRBROTHER

IS AT THE EDGE OF THE GOBI DESERT.

HE'S LOOKING FOR EVIDENCE OF THE INTELLIGENCE NETWORK

THAT KEPT THE MEN IN THE WATCH TOWERS CONNECTED.

OVER THE CREST OF THIS HILL IS AN ANCIENT BEACON TOWER,

AND THE SOLDIERS ON THE BEACON TOWERS HAD ONE JOB,

AND THAT WAS TO LOOK OUT FOR THE ENEMY,

AND WHEN YOU SAW THEM COMING, RAISE THE ALARM.

Narrator: THE CHINESE NEEDED A WAY TO DEFEND

AGAINST THE NOMADS' LIGHTNING SPEED.

THEIR SOLUTION -- SIGNALING.

EACH OF THESE FLAGS REPRESENTED 500 HORSEMEN.

AND SO IN THIS CASE, YOU HAVE THREE FLAGS.

SO THAT MEANS 1,500 HORSEMEN COMING ON THE HORIZON.

Narrator: THE SIGNALING SYSTEM ALLOWED CHINESE INTELLIGENCE

TO TRACK THE NOMADS' RAPID MOVEMENTS.

SO I'M HOPING THAT THE GUYS AT THE NEXT TOWER

ARE PAYING ATTENTION AND NOTICE

THAT THERE'S 1,500 WARRIORS COMING ACROSS THE HORIZON.

Narrator: THE TOWER GUARDS WOULD ALSO SEND SMOKE SIGNALS

TO RAM THE MESSAGE HOME.

THIS RAPID RESPONSE TO A NOMAD ATTACK

WAS CRUCIAL TO THE DEFENSE OF THE WALL

AND TO THE DEFENSE OF CHINA.

Fairbrother: GREAT WALL'S NOT JUST A DEFENSIVE STRUCTURE.

IT'S ALSO PART OF AN INTELLIGENCE NETWORK.

ON THAT SIDE, NOMADIC WARRIORS

CONSTANTLY LOOKING FOR PLACES

THAT THEY CAN ATTACK WITH SURPRISE.

AND ON THE WALL, THE CHINESE SOLDIERS

LOOKING OUT FOR THE SIGNS OF THAT ATTACK.

IF THEY SEE IT, THEY RAISE THE ALARM DOWN

THE NETWORK OF BEACON TOWERS.

Narrator: THIS SYSTEM OF WATCH TOWERS

AND SIGNALING STATIONS NEEDED TO BE IMPENETRABLE.

STRETCHING RIGHT ALONG CHINA'S NORTHERN FRONTIER

TO ITS END POINT 72 FEET INTO THE YELLOW SEA.

THANKS TO ITS INGENIOUS DESIGN,

THIS STRUCTURE IS STILL STANDING.

KNOWN AS THE DRAGON'S HEAD, SOLID GRANITE STRIPS,

EACH WEIGHING OVER THREE TONS,

PROVIDE THE BULK TO FIGHT OFF THE WAVES.

IRON CLAMPS LOCK THEM SECURELY TOGETHER.

AND JOINTS CARVED INTO THE STONES

FIXED THE LAYERS TIGHT

TO STOP THEM DRIFTING WITH THE TIDE.

NINE LAYERS OF STONE BLOCKS STAND AGAINST THE CRASHING WAVES

TO ENSURE INVADERS CAN'T GET AROUND.

THIS NEARLY 50-FOOT-HIGH TOWER

IS A MONUMENTAL END TO THE GREAT WALL.

THE WALL AND ITS SIGNALING SYSTEM WERE CONNECTED

FROM THIS OCEAN FORTRESS IN THE EAST

TO THE DESERTS IN THE WEST.

IT MEANT THAT THE CHINESE ARMY

WAS FULLY PREPARED TO PROTECT THE ENTIRE COUNTRY.

SOLDIERS WOULD BE MANNING THE BATTLEMENTS

WITH THEIR BOWS AND THEIR CROSSBOWS,

UNLEASHING SHOWERS OF ARROWS

AND CROSSBOW BOLTS DOWN ON THE ENEMY.

Narrator: BUT IN THE MIDST OF A DEADLY ATTACK,

HOW WERE REINFORCEMENTS ABLE TO REACH THESE REMOTE

WATCH TOWERS IN TIME?

Narrator: THE GREAT WALL WAS BUILT AS A DEFENSIVE SHIELD

STRETCHING ACROSS THE VAST LAND OF CHINA.

BUT WHEN UNDER ATTACK,

HOW DID CHINESE REINFORCEMENTS

GET TO ISOLATED WATCH TOWERS ATOP SUCH TOUGH TERRAIN?

ONE OF THE PRIMARY JOBS OF THE GUARDS IN TOWERS

LIKE THAT WAS TO WATCH FOR THE ENEMY.

AS SOON AS THEY WERE SPOTTED,

MAKE AN ALARM SIGNAL TO SUMMON REINFORCEMENTS

TO THIS LOCATION.

Narrator: GREAT WALL HISTORIAN WILLIAM LINDESAY

IS WALKING THE WALL AT JIANKOU NORTH OF BEIJING.

HE'S LOOKING FOR EVIDENCE

THAT REVEALS HOW TROOPS MANEUVERED TO FIGHT OFF RAIDS

AT THE TOP OF MOUNTAIN RIDGES.

PEOPLE OFTEN LOOK AT THIS, AND THEY SAY,

"COME ON, THEY DIDN'T NEED A DEFENSE WALL THERE.

NO ONE IS GONNA ATTACK THIS SPOT."

I AGREE, YOU CAN REALLY APPRECIATE

THAT MORE AS YOU'RE STANDING UNDER IT.

I MEAN, LOOK AT THAT.

IT'S JUST CLINGING TO THE CLIFF FACE.

Narrator: SO WHY DID THE CHINESE BUILD THE WALL

ON THIS STEEP STRETCH?

DID IT HAVE ANOTHER PURPOSE?

THAT IS A MISSING LINK.

IT'S TO JOIN UP THE WALL HERE,

THE WALL OVER THERE, THE WALL OVER THERE.

IT MAKES THE BORDER WALL INTO A BORDER ROAD SYSTEM.

Narrator: WILLIAM BELIEVES THE WALL WAS A ROADWAY

THAT GAVE SUPPORT TROOPS

IMMEDIATE ACCESS TO SOLDIERS UNDER ATTACK.

THIS CONVERTED THE WALL INTO A VAST TRANSPORT NETWORK.

[ WIND RUSHING ]

IT EXTENDED THOUSANDS OF MILES TO CHINA'S WESTERN DESERT,

WHERE IT PERFORMED ITS FINAL FUNCTION:

TO PROTECT CHINESE TRADE.

THE ANCIENT TRADING ROUTE CALLED THE SILK ROAD

STRETCHED THROUGH THE FAR WEST OF CHINA.

THE ROAD WAS THE NATION'S LINK TO THE OUTSIDE WORLD.

RICHARD FAIRBROTHER IS DRIVING ALONG THE SILK ROAD,

HUNTING OUT ITS CONNECTIONS TO THE GREAT WALL.

LIKE SILK ROAD TRAVELERS OF THE PAST,

HE PICKS UP SUPPLIES AT THE MARKET IN DUNHUANG...

...AND HEADS OUT INTO THE HARSH COLD OF THE WESTERN DESERT.

HE'S LOOKING FOR A DESERT FORTRESS.

THAT'S AWESOME.

THIS AMAZING FORT IS OVER 2,000 YEARS OLD.

IT'S RIGHT ON THE SILK ROAD.

IT'S CALLED SHANMACHUNG,

WHICH LITERALLY TRANSLATES AS "HORSE CASTRATION FORT."

IT'S IN A GLORIOUS LOCATION WITH HUGE MOUNTAINS

AND THIS RIVER THAT'S RIPPED THE SIDE OF THE FORT AWAY.

AND IT WAS A PLACE WHERE HORSES WERE CASTRATED

BEFORE BEING ACCEPTED BY THE CHINESE EMPIRE

IN TRADE FOR TEA.

Narrator: THE GREAT WALL AND THE FORTS

ALONGSIDE IT KEPT THE TRADERS ALONG THE SILK ROAD SAFE.

Fairbrother: THE TRADE ALONG THE SILK ROAD WAS CRUCIAL

TO THE CHINESE EMPIRE,

AND THAT'S WHY THEY BUILT THE GREAT WALL

AND ALL OF THESE FORTS DOTTED ALONG IT.

Narrator: BUT INVITING FOREIGN TRADERS

INTO THEIR FORTS MADE THE CHINESE VULNERABLE.

DESPITE THEIR ENTHUSIASM FOR COMMERCE,

THE CHINESE WERE WARY THAT FOREIGN TRADERS

MIGHT ACTUALLY BE NOMAD SPIES.

SO THEY DESIGNED THEIR FORTS

SO THAT JUST ONE FALSE MOVE WOULD RESULT IN A GRUESOME END.

BELOW THE GATEHOUSE, A NARROW PASSAGE FUNNELED VISITORS

INTO THE FEARED PASSAGEWAYS OF DEATH.

THE WALLS CREATED A MAZE FOR THE INTRUDERS TO NAVIGATE.

TRAVERSING RIGHT-ANGLED TURNS,

FORCING THEM INTO THE CONFINED COURTYARD...

THIS NEARLY 33-FOOT-TALL TRAP

WAS DEADLY FOR UNWANTED VISITORS.

AS GUARDS ON THE PARAPETS LOOMED ABOVE WITH WEAPONS,

THIS WAS THE PERFECT GATEWAY TO PROTECT CHINA'S LAND.

THE GREAT WALL WAS A MONUMENTAL PIECE OF MILITARY ENGINEERING

THAT ALLOWED CHINA TO FACE DOWN THE TERROR FROM THE NORTH.

JUST LOOKING AT THE WALL

AND SEEING HOW IT SNAKES OVER THESE MOUNTAINTOPS,

YOU REALIZE THAT IT IS AN INCREDIBLE ACHIEVEMENT.

IT GOES ACROSS CHINA.

Lindesay: THIS IS THE WORLD'S MOST LABOR-INTENSIVE,

MATERIAL-CONSUMING,

AND TIME-CONSUMING CONSTRUCTION IN OUR HISTORY.

I REALLY BELIEVE IT IS THE ULTIMATE WONDER OF THE WORLD.

*

I LOVE THE GREAT WALL.

I MIGHT SOUND A BIT NERDY, BUT I HAVE A SAYING:

"IF YOU'RE TIRED OF THE GREAT WALL,

YOU'RE TIRED OF LIFE."

Narrator: THE GREAT WALL PROTECTED CHINA'S FARMERS...

...AND PROJECTED THE NATION'S IMPERIAL POWER ALONG THE WORLD'S

MOST IMPORTANT TRADE ROUTE.

THE FEELING OF HISTORY, OF BEING HERE,

BEING PERHAPS THE ONLY PERSON WHO'S BEEN HERE IN SOME TIME,

IS HARD TO DESCRIBE.

IT'S JUST AWESOME.

Narrator: FROM A SELF-CEMENTING EARTH WALL

TO AN IMPENETRABLE LINE OF BRICK FORTIFICATIONS,

DEFENSIVE BATTLEMENTS, DEADLY MAZES,

AND A WALKWAY THAT EXPANDS A COUNTRY,

COMBINE TO CREATE THE ULTIMATE ACHIEVEMENT

IN MILITARY ARCHITECTURE...

AT ONE OF THE MOST AWE-INSPIRING STRUCTURES

EVER CREATED.