Original subtitles

*

Narrator: THE GREAT GOTHIC CATHEDRALS OF EUROPE,

SOARING MEDIEVAL SKYSCRAPERS THAT HOLD AGE-OLD SECRETS.

HOW DID THEIR CREATORS BUILD SO HIGH

USING ONLY SIMPLE TOOLS?

WHAT BELIEFS INSPIRED THEM TO REACH FOR THE SKY?

Pritchard: IT IS AN INCREDIBLE BUILDING.

THE HEIGHT, THE FOOTPRINT, THE PRESENCE --

IT'S REALLY SPECTACULAR.

Narrator: AND CAN NEW TECHNOLOGY UNLOCK THE SECRET SCIENCE

THAT PROTECTS THESE STONE GIANTS FROM DISASTER?

Stinnesbeck: THEY HAD TO BE AFRAID

THAT THE EARTH PRESSURE WOULD BRING THE PITS TO COLLAPSE.

*

Narrator: THE ONLY WAY TO SOLVE THESE MYSTERIES

IS TO BLOW APART THESE MIGHTY, MEDIEVAL MEGASTRUCTURES

STONE BY STONE.

*

DIVING DEEP THROUGH THEIR WALLS, VAULTS, AND FOUNDATIONS

WILL HELP US UNEARTH THE ASTONISHING ENGINEERING SECRETS

AT THE HEART OF THESE AGE-OLD WONDERS.

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

CAPTIONS PAID FOR BY DISCOVERY COMMUNICATIONS

THE GERMAN CITY OF COLOGNE

ON THE BANKS OF THE MIGHTY RHINE RIVER...

*

THIS IS THE HOME OF THE WORLD'S MOST AMBITIOUS MEGASTRUCTURE.

*

COLOGNE CATHEDRAL...

...A MYSTERIOUS MONUMENT THAT BEGAN LIFE IN THE MIDDLE AGES.

750 YEARS AGO, THE PEOPLE OF THIS CITY

EMBARKED ON A COLOSSAL CHALLENGE

TO BUILD THE TALLEST CATHEDRAL OF THE DAY...

*

...20 TIMES HIGHER THAN THE WOODEN BUILDINGS IN TOWN.

THE SHEER SCALE OF THIS CHURCH

ASTOUNDS MODERN EXPERTS WHO TRY TO UNLOCK ITS SECRETS.

THE AMAZING THING ABOUT THE COLOGNE CATHEDRAL IS,

IF YOU GO BACK IN TIME, SOMEONE ACTUALLY HAD THE VISION

TO DESIGN AND CONCEIVE A BUILDING OF THIS SIZE,

AND IT'S SPECTACULAR.

COLOGNE CATHEDRAL IS A 130,000-TON STONE GIANT.

THERE'S ENOUGH GLASS IN THE WALLS

TO CLAD A 30-STORY SKYSCRAPER.

HUGE STONE RIBS PROP UP THE CEILING...

...AS WELL AS THE 600-TON LEAD ROOF.

STRETCHING NEARLY 525 FEET INTO THE SKY,

TWO ENORMOUS TOWERS ONCE MADE THIS CHURCH

THE TALLEST BUILDING ON EARTH.

SO HOW DID THEY PULL OFF THIS MEDIEVAL MARVEL?

HISTORIANS KNOW SURPRISINGLY LITTLE

ABOUT WHAT ACTUALLY WENT ON

DURING THE EARLY DAYS OF COLOGNE'S CONSTRUCTION.

FEW RECORDS HAVE SURVIVED.

*

NOW ARCHITECT DOUG PRITCHARD

IS REDISCOVERING HOW THE CATHEDRAL WAS BUILT

BY STRIPPING IT APART STONE BY STONE.

[ BELL TOLLS ]

DOUG'S GOT THE PERFECT TOOL TO DO THIS --

A DIGITAL LASER SCANNER.

THIS MACHINE WILL ALLOW HIM TO REVEAL THE BUILDING

IN UNPRECEDENTED FORENSIC DETAIL.

THE SCANNER IS REALLY QUITE INCREDIBLE.

IT CAN GENERATE

APPROXIMATELY 1 MILLION DIMENSION POINTS PER SECOND.

Narrator: THE WAY THAT THE SCANNER WORKS

IS THAT IT DOES A 360-DEGREE SWEEP.

IT WILL SHOW THINGS LIKE THE DEPTH OF THE VAULTS,

THE SIZE OF THE COLUMNS, IN A VERY PRECISE WAY.

WE TAKE ALL THAT DATA TOGETHER,

AND THE RESULT IS YOU HAVE A 3D MAP OF THE CATHEDRAL.

*

Narrator: TODAY, DOUG'S ADDING

ANOTHER IMPORTANT PIECE TO HIS PUZZLE.

GUTEN TAG.

HI.

HE'S ON HIS WAY TO THE CENTRAL BALCONY.

IF HE CAN USE SCANNING

TO EXPOSE THE CATHEDRAL'S UNDERLYING STRUCTURE,

HE CAN START TO DISSECT HOW IT WORKS.

*

Pritchard: ONE OF THE GREAT THINGS ABOUT LASER SCANNING

IS THAT YOU COULD PULL THE DATA APART.

LET'S USE THE SCANNED DATA TO EXPLAIN THE ARCHITECTURE --

HOW THE BUILDING STANDS UP, HOW THE ENGINEERING WORKS.

Narrator: DOUG'S SCANNER FIRES AN INVISIBLE LASER BEAM

AS FAR AWAY AS 614 FEET.

IT RECORDS EACH TIME THE BEAM HITS SOMETHING SOLID

AND BOUNCES BACK...

...AND THEN TURNS THIS DATA INTO INCREDIBLY DETAILED IMAGES

SO THAT DOUG CAN STUDY THE STRUCTURE FROM EVERY ANGLE.

Pritchard: IN TOTAL, RIGHT NOW, WE'RE AT ABOUT 660 SCANS.

PROBABLY, BY THE END OF THIS WEEK, ADD IN ANOTHER 20 OR 30.

Narrator: DOUG NOW NEEDS TO CRUNCH A HUGE VOLUME OF DATA.

BUT HE CAN ALREADY START TO SEE THE MASTER PLAN

OF THE PEOPLE WHO BUILT THIS INCREDIBLE MONUMENT.

THE TWO TALL TOWERS ARE VISIBLE FOR MILES.

AT THE TOP, THE SPIRES ARE OPEN TO CUT DOWN WIND RESISTANCE.

AND AT THE BOTTOM, THE WALLS ARE ROCK-SOLID

TO BEAR THE ENORMOUS WEIGHT OF THE TOWERS.

BUT THE CHURCH BEHIND IS COMPLETELY DIFFERENT.

UNDER THE SKIN SITS A SKELETON OF SLENDER STONE ARCHES.

INCREDIBLY, IT LOOKS LIKE THE CORE OF A MODERN SKYSCRAPER,

YET THIS IS THE BRAINCHILD OF MEDIEVAL MASTER BUILDERS --

MEN WHO LIVED 700 YEARS AGO.

SO HOW DID COLOGNE CITIZENS EVEN BEGIN TO IMAGINE

THAT SUCH A TALL BUILDING COULD BE POSSIBLE?

*

200 MILES AWAY, IN NORTHERN FRANCE,

ANOTHER TEAM HUNTS FOR CLUES AT AN EVEN OLDER CATHEDRAL.

*

THIS IS AMIENS -- THE BLUEPRINT FOR COLOGNE.

*

THIS SOARING CHURCH HAS DOMINATED THE CITY'S SKYLINE

FOR NEARLY 800 YEARS.

IT'S THE TALLEST COMPLETE CATHEDRAL IN FRANCE.

*

INVESTIGATOR GUILLAUME CARON USES LASER TECHNOLOGY

TO UNLOCK HOW COLOGNE'S PREDECESSOR WAS BUILT.

*

I WAS BORN, ACTUALLY, IN THE CITY,

SO I KNOW THE SYMBOLIC ASPECT OF THIS CATHEDRAL.

*

Narrator: GUILLAUME IS HOPING TO FIND TINY CLUES

THAT MIGHT HELP RECONSTRUCT AMIENS' LOST ORIGINAL DESIGN.

Caron: CURRENTLY, THERE IS NOT ANY ACTUAL MAP OF THE CATHEDRAL,

SO WHAT WE ARE DOING WITH THIS KIND OF DEVICE

IS TO MEASURE IT VERY PRECISELY

IN ORDER TO HAVE THE FIRST REAL, ACTUAL MAP OF THE CATHEDRAL.

Narrator: AMIENS' CONSTRUCTION BEGAN IN 1220.

IT'S ONE OF A HANDFUL OF CATHEDRALS CLOSE TO PARIS

WHOSE ARCHITECTS DREAMED OF BUILDING CLOSER TO GOD.

THEY WANTED TO BUILD THE HIGHEST AND THE WIDEST CATHEDRAL

BECAUSE AT THAT TIME IN THE MIDDLE AGES,

IT WAS LIKE A RACE BETWEEN THE DIFFERENT CITIES IN FRANCE

TO BUILD THE MOST IMPORTANT CATHEDRAL.

Narrator: GUILLAUME'S SCANS REVEAL

THAT THE CENTRAL ARCH IS 131 FEET HIGH,

BUT THE COLUMNS ARE SURPRISINGLY THIN.

Caron: FROM THIS SCAN PREVIEW,

WE CAN LOOK AT THE DETAILS THAT WERE ACQUIRED BY THE DEVICE.

FOR INSTANCE, THE COLUMNS HERE IN THE TRANSEPT.

Narrator: BUT UNTIL THE 12th CENTURY,

COLUMNS THIS TALL AND SLENDER WOULD HAVE BEEN TOO WEAK

TO SUPPORT SUCH AN ENORMOUS BUILDING.

SO HOW DID FRENCH ARCHITECTS SOLVE A PUZZLE

THAT HAS BAFFLED EVEN THE GREAT BUILDERS OF ANCIENT ROME?

THE KEY IS IN THE SHAPE OF THE ARCHES.

IN A CLASSICAL ROMAN ARCH,

THE STONES AT THE TOP PUSH SIDEWAYS AGAINST THE COLUMNS.

AS YOU BUILD HIGHER, THEY START TO BUCKLE...

AND THE CEILING WILL COLLAPSE.

BUT FRENCH ENGINEERS REALIZED

THAT IF YOU MAKE THE ARCH POINTED...

THE FORCES NOW FLOW DOWN TOWARDS THE STRONG BASE OF THE COLUMN.

NOW THE SAME COLUMNS CAN TAKE MORE WEIGHT.

THE ARCH CAN BE MUCH TALLER AND THE CHURCH MUCH BIGGER.

AMIENS, WITH ITS POINTED ARCHES,

SHOWED COLOGNE CITIZENS A GLIMPSE OF WHAT WAS POSSIBLE.

*

BUT WHAT DROVE THE GERMANS TO BUILD EVEN HIGHER?

*

THE SECRET LIES AT THE HEART OF COLOGNE CATHEDRAL,

INSIDE THIS GOLDEN SHRINE.

SOME BELIEVE IT HOLDS THE BONES OF THE THREE WISE MEN.

PETER FUSSENICH

IS THE CATHEDRAL'S CURRENT CHIEF ARCHITECT.

HE OVERSEES AN ARMY OF MORE THAN 70 PEOPLE

WHO KEEP THIS BUILDING RUNNING.

*

TODAY, THE CHURCH ATTRACTS 6 MILLION VISITORS A YEAR.

*

BUT PETER THINKS THAT IN THE MIDDLE AGES,

IT WAS ALSO THIS TOMB THAT WAS THE STAR ATTRACTION.

[ FUSSENICH SPEAKING GERMAN ]

Interpreter: THE SHRINE IS, OF COURSE, ONE OF THE REASONS

WHY THEY BUILT COLOGNE CATHEDRAL IN THE FIRST PLACE.

IT'S LESS THE SHRINE -- THAT WAS BUILT LATER.

IT'S MORE WHAT'S INSIDE IT.

I'M TALKING ABOUT THE BONES OF THE THREE WISE MEN.

THIS HOLY RELIC ARRIVED IN COLOGNE IN 1164

AND IMMEDIATELY TRIGGERED A HUGE STREAM OF PILGRIMS TO THE CITY.

THAT MEANT THAT VERY QUICKLY, THE OLD CHURCH BECAME TOO SMALL,

WHICH IS WHY THEY HAD TO BUILD A BIGGER CATHEDRAL.

Narrator: THIS MYSTERIOUS HOLY SHRINE

INSPIRED COLOGNE'S FOUNDERS TO START WORK ON A CATHEDRAL SO BIG

THAT THEY KNEW THEY WOULD NEVER SEE IT FINISHED

IN THEIR LIFETIMES.

[ FUSSENICH SPEAKING GERMAN ]

Interpreter: THIS IS SOMETHING

THAT'S STILL IMMENSELY FASCINATING FOR US TODAY.

COLOGNE CATHEDRAL

IS ONE OF HUMANITY'S FIRST-EVER MULTIGENERATIONAL PROJECTS --

SOMETHING YOU HAVE TO HAND DOWN TO THE NEXT GENERATION

AND HAVE FAITH THAT THEY WILL ACTUALLY CARRY ON BUILDING IT.

Narrator: THESE MEN HOPED THAT THEIR CHILDREN AND GRANDCHILDREN

COULD OVERCOME THE NEXT HUGE OBSTACLE...

...HOW WOULD THEY BUILD A CHURCH WITH ENOUGH ROOM

FOR 20,000 WORSHIPPERS MADE FROM FRAGILE WALLS OF GLASS?

*

Narrator: COLOGNE CATHEDRAL IS A MYSTERIOUS MEDIEVAL SKYSCRAPER.

IT COVERS 86,000 SQUARE FEET.

HOW DID HER CREATORS ILLUMINATE A CHURCH THIS BIG

WITH HEAVENLY LIGHT...

HUNDREDS OF YEARS BEFORE ELECTRICITY?

THE ANSWERS ARE HIDDEN DEEP

WITHIN THE FABRIC OF THE CATHEDRAL.

THE TOWERS REST ON THICK, STONE PILLARS

TO STOP THEM FROM COLLAPSING.

BUT THE MAIN HALL OF THE CHURCH IS MUCH MORE OPEN.

THERE'S ENOUGH GLASS HERE TO COVER A FOOTBALL FIELD.

THE UPPER WALLS IN THE MIDDLE ARE ALMOST ENTIRELY GLASS,

JUST INCHES THICK.

AND THEY'RE CROWNED BY A MASSIVE LEAD ROOF.

SO HOW DID MEDIEVAL ENGINEERS CONSTRUCT WINDOWS SO BIG,

SO FRAGILE, YET SO STRONG?

IN THE MIDDLE AGES,

CRAFTSMEN HAD NO WAY TO MAKE HUGE, FLAT SHEETS OF GLASS.

*

ULRIKE BRINKMANN STUDIES THE INGENIOUS SOLUTION

THAT ALLOWED THEM TO PUSH THE BOUNDARIES OF TECHNOLOGY.

*

MEDIEVAL GLASSMAKERS DIVIDED UP EACH WINDOW INTO PANELS.

THEY MADE THEM FROM TINY STAINED-GLASS FRAGMENTS

HELD TOGETHER BY LEAD.

MEDIEVAL GLASS IS BLOWN BY MOUTH, BY GLASSMAKERS.

THEY HAVE A LARGE GLASS PIPE,

AND SO THE SIZE OF THE GLASS PANELS

THAT ARE USED FOR THE GLASS PAINTERS IS LIMITED.

YOU SEE, THE VERY, VERY DARK DEPOSITS ON THE GLASSES --

IN THIS CASE, LUCKILY, THEY CAN BE EASILY REMOVED.

*

Narrator: THE FRAGMENTS STILL LOOK DARK AFTER CLEANING,

BUT THEY COME ALIVE IN THE LIGHT.

LIGHT WAS A MATERIAL IN THE MEDIEVAL UNDERSTANDING,

AND HOW LIGHT FOUGHT THROUGH ANOTHER MATERIAL, LIKE GLASS,

WITHOUT DISTURBING THE GLASS, WAS WITHOUT ANY EXPLANATION.

Narrator: THESE EXQUISITE DETAILS

WOULD HAVE BEEN IMPERCEPTIBLE

TO WORSHIPPERS ON THE CATHEDRAL FLOOR.

BUT THIS KALEIDOSCOPE OF GLASS CREATES THE IMPRESSION

OF A CHURCH REACHING TOWARDS HEAVEN.

Brinkmann: ENTERING THE CATHEDRAL IN MEDIEVAL TIMES --

IT MUST HAVE BEEN BREATHTAKING.

THE SUN FALLING THROUGH AND LIGHTING THE INTERIOR --

THIS WAS VERY IMPRESSIVE.

THEY ARE STILL BREATHTAKING TODAY,

AND EVEN MORE IN THOSE DAYS,

WHEN PEOPLE USED TO LIVE IN SMALL AND DARK HOUSES.

*

Narrator: BUT THE EXTREME HEIGHT OF THESE WINDOWS

CREATES A SERIOUS PROBLEM.

POINTED ARCHES HELP MAKE TALLER, MORE ELEGANT CHURCHES

WITH BIG WINDOWS FROM TOP TO BOTTOM.

BUT BUILD TOO HIGH, AND THE STRUCTURE COLLAPSES.

SUPPORTING WALLS, CALLED BUTTRESSES,

COULD HELP TAKE THE STRAIN,

ONLY THEY'D BLOCK OUT LIGHT AND CUT ACROSS THE AISLES.

MEDIEVAL ENGINEERS DISCOVERED

THAT IF THEY BUILD COLUMNS ON THE OUTSIDE

WITH HIGH BEAMS REACHING ACROSS,

THEY COULD BUILD WHAT ARE KNOWN AS FLYING BUTTRESSES.

NOW THEY COULD INSTALL HUGE WINDOWS

TO BRING THEM CLOSER TO GOD AND LET IN HEAVENLY LIGHT.

THESE FLYING BUTTRESSES

HELP SUPPORT THE WALLS AND ROOF FROM THE OUTSIDE,

BUT WHAT STOPS THE CEILING FROM CRASHING DOWN INSIDE THE CHURCH?

HOW DOES IT APPEAR TO HANG IN MID AIR?

*

WOLFGANG KUPPER IS ONE OF 20 EXPERT STONEMASONS AT COLOGNE.

HE KNOWS THAT WORKING WITH THE SOFT LIMESTONE

REQUIRES COMPLETE PRECISION.

Interpreter: WITH THIS SAW BLADE I BORROWED

FROM THE METAL WORKERS, I CAN EASILY CUT INTO THE STONE.

Narrator: THE STONEMASONS ARE LIKE SURGEONS

WHO CARE FOR A 750-YEAR-OLD PATIENT.

TODAY, WOLFGANG HAS THE CHALLENGE

OF REPLACING A STONE BLOCK CALLED A BALDACHIN.

[ SPEAKING GERMAN ]

Interpreter: AT THE MOMENT, I'M WORKING ON THIS FINIAL.

I'LL HAVE TO CARVE OUT THESE GAPS

AND REMOVE THE MATERIAL IN BETWEEN

TO BRING OUT THESE LEAVES -- EXTREMELY SMALL FEATURES.

Narrator: THE ORIGINAL STONE THAT FORMED PART OF THE WALL

IS DAMAGED BEYOND REPAIR.

Interpreter: THIS WAS DAMAGED IN WORLD WAR II.

THE FRONT PART OF IT IS COMPLETELY GONE.

ALL THAT'S LEFT IS THE BACK END.

Narrator: CARVING THIS COPY

WILL TAKE WOLFGANG A YEAR AND A HALF TO FINISH.

*

DID WOLFGANG'S MEDIEVAL PREDECESSORS'

METICULOUS ATTENTION TO DETAIL

CONTRIBUTE TO THE CATHEDRAL'S INCREDIBLE DURABILITY?

*

Narrator: STONEMASONS AT COLOGNE CATHEDRAL

ARE REVEALING THE INNOVATIVE DESIGN

OF THIS SOARING MEDIEVAL SKYSCRAPER.

INSTEAD OF THICK, STONE WALLS TO CARRY THE CEILING,

THEY CARVED POINTED ARCHES

AND JOINED THEM TOGETHER LIKE A RIB CAGE.

IN BETWEEN, THEY PUT JUST A THIN LAYER OF BRICKS

THAT FORMS A SMOOTH CEILING CALLED A RIB VAULT.

SLENDER COLUMNS CHANNEL THE WEIGHT OF THIS VAULT

DOWN TO THE GROUND.

THIS WAY, THE CEILING DOESN'T NEED SUPPORT.

IT SUPPORTS ITSELF.

THE FORCES ON THIS VAULTED CEILING ARE ENORMOUS.

AND JUST A FEW STONES OUT OF PLACE CAN SPELL DISASTER.

*

THE OLDER CATHEDRAL OF AMIENS, IN FRANCE,

REVEALS THE RISKS OF THIS AUDACIOUS DESIGN.

*

LASER-SCANNING EXPERT GUILLAUME CARON

IS AT AMIENS TO INVESTIGATE DAMAGE TO THE RIB VAULTS.

*

WE HAVE, ON THE CEILING, A BIG CRACK.

THAT'S WHERE, WITH OUR LASER SCANNER, WE ARE ABLE TO MEASURE.

THIS IS THE SCANNING RESULT.

Narrator: GUILLAUME DISCOVERS THAT THIS CRACK

IS ABOUT TWO INCHES WIDE.

THERE IS ALSO OTHER CRACKS

INSIDE THE MAIN NAVE OF THE CATHEDRAL,

SO ON THE TOP OF THIS TALL WINDOW.

Narrator: GUILLAUME CAN'T SAY EXACTLY

WHAT'S CAUSING EVERY CRACK.

BUT EXPERTS THINK THAT AMIENS HAS A SERIOUS DESIGN FLAW.

OUTSIDE, THE FLYING BUTTRESSES ARE TOO HIGH

AND CAN'T TAKE THE STRAIN OF THE ROOF.

SO THE SIDES HAVE BUCKLED, TEARING THE RIB VAULTS APART.

SO IS THE DAMAGE GETTING WORSE?

Caron: FROM OUR LATEST RESULTS,

WE MEASURED THAT THIS CRACK IS ABOUT FIVE CENTIMETERS,

AND WE COMPARED THAT

WITH MEASURES WE MADE FOUR YEARS BEFORE.

ACTUALLY, THERE IS NO INCREASING OF THIS THICKNESS,

AND THIS IS GOOD NEWS FOR THE CATHEDRAL.

*

Narrator: IN GERMANY, AT COLOGNE CATHEDRAL,

THE CEILING LOOKS PERFECT.

BUT IS IT?

*

DOUG PRITCHARD VENTURES INSIDE THE ROOF TO INVESTIGATE.

HE WANTS TO LASER-SCAN COLOGNE'S RIB VAULT FROM ABOVE.

Pritchard: RIGHT NOW, WE'RE BETWEEN THE CROSSING

AND THE OLDER PART OF THE BUILDING -- THE CHOIR.

THE WAY THAT THE SCANNING IS GONNA WORK

IS I'LL HAVE THE SCANNER

POSITIONED ALL THE WAY AROUND THIS OPENING AREA HERE,

AND WITH THAT DATA,

I'LL TAKE THE DATA FROM BELOW THAT WAS SCANNED EARLIER

AND COMBINE THE TWO.

AND WITH THAT,

I'M ABLE TO VIRTUALLY SLICE THROUGH THE CATHEDRAL.

*

Narrator: DOUG HOPES HIS SCANS

WILL EXPOSE THE CATHEDRAL'S INNER WORKINGS

AND SHOW THEM LIKE NEVER BEFORE.

*

Pritchard: I THINK THIS IS A FANTASTIC IMAGE

IN THAT IT CLEARLY, CLEARLY EXPLAINS THE ARCHITECTURE

OF THE CATHEDRAL.

Narrator: THE FINISHED 3D IMAGE

CAPTURES THE CATHEDRAL WITH EXTREME ACCURACY.

AND WHAT I FOCUSED ON HERE IS WHERE WE'RE CURRENTLY STANDING,

AND WHAT'S INTERESTING IS THE RIB VAULTS

ARE ACTUALLY ALMOST LIKE A THIN MEMBRANE,

BUT THE ACTUAL ENGINEERING AND STRUCTURE

IS BEING PICKED UP BY THE POINTED ARCHES.

YOU HAVE THE COLUMNS,

WHICH ARE TAKING THE WEIGHT DOWN TO THE FOUNDATION.

YOU ALSO HAVE THE FLYING BUTTRESSES,

WHICH ARE PRESSING INWARD SLIGHTLY,

AND SO THEY'RE ALL IN HARMONY

IN TERMS OF HOW THE STRUCTURE OF THE CATHEDRAL WORKS.

Narrator: DOUG'S SCANS PRESENT AN EVEN MORE INTRIGUING MYSTERY.

HOW DID ANCIENT ENGINEERS BUILD A RIB VAULT

OVER 131 ABOVE THEIR HEADS WITHOUT IT CRASHING DOWN?

INVESTIGATORS THINK THAT THE BUILDERS FIRST PUT UP

WOODEN SCAFFOLDS ALL THE WAY TO THE TOP OF THE ARCHES.

THEY STACKED STONE BLOCKS ON TOP

TO BUILD THE RIBS WITH EXTREME PRECISION...

...SO THE CENTERPIECE WOULD FIT PERFECTLY.

THEN THEY FILLED THE GAPS BETWEEN THE RIBS

WITH LIGHTWEIGHT BRICKS AND COVERED THEM WITH MORTAR.

FINALLY, THEY REMOVED THE WOODEN SCAFFOLD,

PRAYING THAT THEIR CEILING WOULD HOLD.

COLOGNE'S BUILDERS HAD CREATED A PERFECTLY BALANCED SKYSCRAPER

HUNDREDS OF YEARS BEFORE THOSE OF THE MODERN ERA.

*

BUT HOW HAS THIS COLOSSAL CATHEDRAL

SURVIVED CENTURIES OF WIND, RAIN, AND NATURAL DISASTER?

*

*

Narrator: COLOGNE CATHEDRAL IS A REMARKABLE SURVIVOR.

THIS STONE GIANT

STANDS IN ONE OF EUROPE'S MOST ACTIVE EARTHQUAKE REGIONS.

*

MORE THAN 120 QUAKES

HAVE HIT THE SURROUNDING AREA OVER THE LAST 300 YEARS,

CAUSING MODERN BUILDINGS TO CRUMBLE.

SO WHAT'S THE SECRET?

HOW HAS THIS MYSTERIOUS STRUCTURE

SURVIVED LIFE IN THE DANGER ZONE?

*

KLAUS-G. HINZEN IS A SEISMOLOGIST

AT THE UNIVERSITY OF COLOGNE.

HE LEADS A TEAM OF SPECIALISTS TO THE CATHEDRAL ROOF.

THEY'VE COME TO RETRIEVE DATA

REVEALING HOW THE CATHEDRAL REACTS DURING AN EARTHQUAKE.

Hinzen: WE STARTED TO MONITOR THE CATHEDRAL IN 2006.

FROM TIME TO TIME, WE HAVE TO DO MAINTENANCE

AND TO SEE HOW THE STATION IS WORKING.

CAN YOU GIVE THE CONTROL-F?

Narrator: THESE INSTRUMENTS ARE MOTION SENSORS

THAT WILL PICK UP EVEN THE TINIEST MOVEMENT

IN THE FABRIC OF THE CHURCH.

*

Hinzen: ON THE LEFT, ON THE SMALL SCREEN HERE,

WE SEE THE GROUND MOTION THAT IS JUST BEING RECORDED

HERE AT THIS MOMENT,

AND WE CAN SEE THAT IT IS ACTUALLY WORKING.

I JUST HAVE TO STAMP A LITTLE BIT WITH MY FOOT.

*

YOU SEE, IT IS RATHER SENSITIVE.

WE ARE A COUPLE OF METERS AWAY FROM THE SENSOR,

BUT ANYWAY, YOU PICK UP THE SIGNAL.

Narrator: THIS EQUIPMENT IS HELPING KLAUS

TO PREDICT WHAT WOULD HAPPEN IN A BIG QUAKE.

Hinzen: WE HAVE HAD SEVERAL STRONG EARTHQUAKES

WITH MAGNITUDES BETWEEN 6.5 AND 7

IN THE PAST 20,000, 30,000 YEARS IN THE AREA.

AND GEOLOGICALLY, THIS IS A VERY SHORT TIME SPAN,

AND SUCH AN EARTHQUAKE COULD HAPPEN ANY TIME.

IT COULD HIT TODAY OR NEXT WEEK.

Narrator: HE FEARS THAT A MAJOR EARTHQUAKE

COULD SHATTER THESE CEILING VAULTS.

BUT KLAUS' WORK REVEALS

THAT THE TOWERS WOULD BEHAVE VERY DIFFERENTLY.

Hinzen: HERE WE SEE A RECORDING EXAMPLE OF A REAL EARTHQUAKE.

IT WAS ABOUT 90 KILOMETERS AWAY FROM THE CATHEDRAL

AND HAD A MAGNITUDE OF 4.5.

THE RED TRACES ARE THE ONES THAT WE RECORDED

IN THE BASEMENT OF THE CATHEDRAL,

WHICH BASICALLY IS THE INPUT SIGNAL,

WHICH COMES INTO THE BUILDING, AND FOR COMPARISON,

THE BLUE SIGNALS THAT WE SEE HERE --

THIS IS THE MOTION OF THE TOWER.

WE SEE THE TOWER STARTS SWINGING BACK AND FORTH,

AND THIS MOTION OF THE TOWER, THEN, LASTS FOR SEVERAL MINUTES,

THAT WE CAN RECORD IT.

Narrator: IT'S AN ASTONISHING MYSTERY.

HOW DID COLOGNE'S ARCHITECTS CREATE TOWERS

THAT SWING LIKE PENDULUMS

INSTEAD OF CRUMBLING TO THE GROUND?

EVEN WITH ALL THESE SLENDER COLUMNS,

THIS BUILDING IS NO FEATHERWEIGHT.

MEDIEVAL ENGINEERS TOOK CARE OF THIS WEIGHT

WITH SECRET STRUCTURES HIDDEN UNDERGROUND.

THEY LAYERED 120,000 TONS OF ROCKS

INTO SUPER MASSIVE FOUNDATION PILLARS

STRETCHING DEEP UNDERGROUND.

JUST AS MUCH STONE LIES BENEATH AS SOARS ABOVE,

BALANCING THIS CATHEDRAL PERFECTLY.

COLOGNE'S FOUNDERS PROTECTED THEIR CATHEDRAL

WITH DEEP FOUNDATIONS,

BUT IN THE MIDDLE AGES,

MOST PEOPLE SAW EARTHQUAKES AS A PUNISHMENT FROM GOD

AND THOUGHT ONLY PRAYERS COULD PREVENT THEM.

SO DID THE CATHEDRAL'S BUILDERS REALLY UNDERSTAND

THE TRUE FORCES OF NATURE AT WORK?

*

ARCHAEOLOGIST RUTH STINNESBECK INVESTIGATES WHAT THEY KNEW

ABOUT THE GROUND THEY WERE BUILDING ON.

*

HER QUEST TAKES HER DOWN TO AN ARCHAEOLOGICAL DIG

UNDERNEATH THE CATHEDRAL FLOOR.

*

HERE, INVESTIGATORS WERE ASTONISHED TO DISCOVER

THAT THIS FOUNDATION PILLAR GOES DOWN 52 FEET.

IT'S AS DEEP AS THE PILLARS

THAT SUPPORT THE EMPIRE STATE BUILDING.

BUT WHAT REALLY SHOCKED THEM IS WHAT THEY FOUND AT THE BOTTOM.

[ BEEPING ]

OH, YES. THAT'S THE BEEP.

Narrator: WATER.

SO WHY DID THE MEDIEVAL DIGGERS

RISK FLOODING THEIR OWN CONSTRUCTION SITE?

RUTH THINKS IT'S BECAUSE THEY DISCOVERED

AN EVEN GREATER DANGER...

SAND.

THE CITY OF COLOGNE AND ALSO THE CATHEDRAL

IS JUST STANDING ON SAND AND GRAVEL,

AND THAT'S THE SAND WE ALSO HAVE DOWN HERE.

YOU LOOK, IT'S NOTHING SOLID, JUST SAND.

*

Narrator: THE BUILDERS HERE WORRIED

THAT THE CATHEDRAL WOULD SINK INTO COLOGNE'S SOFT SAND.

SO THEY DECIDED TO PUSH THEIR FOUNDATIONS AS DEEP AS POSSIBLE

TO MINIMIZE ANY RISK.

IT MUST HAVE BEEN LIKE DIGGING ON A BEACH.

SO HOW DID THEY DO IT?

IF WORKERS TRIED TO EXCAVATE A HOLE

WIDE ENOUGH AND DEEP ENOUGH IN ONE TRY,

THE LOOSE SAND WOULD HAVE CAVED IN AND CRUSHED THEM.

SO THEY DUG ONLY IN SHALLOW STEPS...

SHORING UP THE SIDES WITH WOODEN BOARDS,

STOPPING JUST BEFORE THE WATER LEVEL.

THEY PILED IN LAYERS OF VOLCANIC ROCKS AND MORTAR

TO BUILD UP MIGHTY STONE PILLARS OVER FIVE STORIES TALL.

THESE FORMED ROCK-SOLID FOUNDATIONS,

SUPPORTING 120,000 TONS OF STONE TO THIS VERY DAY.

*

ARCHAEOLOGISTS HAVE UNEARTHED THE STARTLING REMAINS

OF THIS ANCIENT CONSTRUCTION SITE.

*

OVER HERE, WE HAVE THE FOUNDATION

OF ONE OF THE PILLARS UPSTAIRS IN THE CATHEDRAL,

AND WHAT WE SEE IS A MORTAR SURFACE.

Narrator: RUTH BELIEVES THAT THESE SPLINTERS

ARE THE REMAINS OF THE WOODEN BOARDS

THE BUILDERS USED TO HOLD BACK THE SAND.

Stinnesbeck: YOU SEE, ONE PLANK STARTS OVER HERE TO THERE,

AND THE NEXT PLANK FROM OVER HERE...

TO HERE.

WHEN I LOOK AT THE WOOD,

I TRY TO IMAGINE HOW THE PEOPLE MUST HAVE FELT

WHEN THEY WORKED DOWN HERE IN THOSE VERY DEEP AND DARK PITS,

AND YEAH, THEY HAD TO BE AFRAID THAT THE EARTH PRESSURE

WOULD BRING THE PITS TO COLLAPSE,

AND ONLY THOSE PLANKS WOULD PREVENT IT

FROM SUCH A CATASTROPHE.

AND SO I THINK WHEN YOU STAND DOWN HERE,

YOU CAN FEEL HOW THE PEOPLE MIGHT HAVE FELT AT THAT TIME.

Narrator: ARCHAEOLOGISTS LIKE RUTH

CONTINUE TO INVESTIGATE THIS INTRIGUING UNDERWORLD.

*

BUT THERE'S ANOTHER SURPRISE ABOVE GROUND.

BEHIND THE BEAUTIFUL VAULTED CEILING

LIES A STRANGE STRUCTURE.

WHAT COULD IT BE?

*

Narrator: COLOGNE CATHEDRAL IS THE MOST AMBITIOUS

MEDIEVAL CATHEDRAL IN THE WORLD.

THIS TOWERING STRUCTURE CONCEALS MANY SURPRISING SECRETS.

*

THERE'S MUCH MORE TO IT THAN MEETS THE EYE.

UNDER THE HOOD OF THIS STONE GIANT

HIDES A STRUCTURE THAT LOOKS OUT OF PLACE.

IT'S A GIGANTIC FRAMEWORK OF SLENDER, WROUGHT-IRON STRUTS

THAT HOLD UP THE 600-TON ROOF.

UNTIL THE EIFFEL TOWER,

THIS WAS THE MOST ADVANCED IRON CONSTRUCTION ON THE PLANET.

SO WHAT IS THIS METAL MARVEL

DOING INSIDE A MEDIEVAL BUILDING?

DRAWINGS AND CHRONICLES RECORD THE CONSTRUCTION WORK

ON THE CATHEDRAL GROUND TO A HALT IN 1530.

IT DIDN'T START UP AGAIN FOR MORE THAN 300 YEARS.

SO HOW DID 19th-CENTURY CRAFTSMEN

KNOW HOW TO FINISH THE BUILDING?

CHIEF ARCHITECT PETER FUSSENICH UNCOVERS THE ANSWER...

...A FADED 13th-CENTURY DESIGN FOR THE TWO TOWERS

THAT WAS ONCE LOST

BUT REDISCOVERED BY CHANCE NEARLY 600 YEARS LATER.

Fussenich: THE ARCHITECTS OF COLOGNE CATHEDRAL

IN THE 19th CENTURY

WERE VERY LUCKY TO FIND THAT MEDIEVAL PLAN,

TO HAVE THE POSSIBILITY TO BUILD THE FACADE

SO THAT THEY COULD FINALLY FINISH THE DREAMS

OF THE MEDIEVAL ARCHITECTS.

Narrator: THE SKETCH, CALLED "PLAN F",

LOOKS LIKE A MODERN BLUEPRINT,

BUT IT HAS NO DIMENSIONS, NO INSTRUCTIONS.

THIS "PLAN F" WAS NOT MEANT AS A CONSTRUCTION PLAN.

IT WAS A PLAN TO CONVINCE THOSE WHO FINANCED THIS CATHEDRAL,

OF COURSE.

Narrator: SO HOW GOOD A JOB DID THE 19th-CENTURY BUILDERS DO?

STONE RESTORER SOPHIE HOEPNER BELONGS TO AN ARMY OF EXPERTS

WHO UNCOVER HOW THE FINAL BUILDERS

HAD TO MAKE COMPROMISES.

*

SOPHIE AND HER COLLEAGUES ARE ON THEIR WAY

TO FIX A PROBLEM WITH THE FLYING BUTTRESSES

BUILT IN THE 19th CENTURY.

Hoepner: THE WORK OF A STONE RESTORER

IS MAYBE COMPARABLE TO, IN MEDICINE, A DOCTOR.

Narrator: THE MEDIEVAL BUILDERS

PREFERRED TO USE A HARD STONE CALLED TRACHYTE,

BUT THE ROCK IN THESE FLYING BUTTRESSES FROM THE 19th CENTURY

IS SOFT SANDSTONE.

AND IT'S ALREADY STARTING TO CRUMBLE.

WHAT WE CAN SEE HERE, SOME DETERIORATED AREA.

HERE WE HAVE ALL THE RAIN IS COMING FROM ABOVE

AND JUST WASHING.

YOU SEE, IT'S MUCH DRYER,

AND THERE IS A COLLECTION OF DIRT.

YOU GET BLACK APPEARING BECAUSE OF THE POLLUTION IN THE AIR,

AND THESE PARTS WHERE THE STONE IS LIKE SAND,

IT GETS WASHED DOWN.

AND THAT'S WHY IT'S MUCH CLEARER THAN THE REST OF THE STONE.

Narrator: SOPHIE NEEDS TO KNOW HOW BAD THE DAMAGE IS.

*

SO HER FIRST TASK IS TO TEST HOW THE STONE REACTS TO RAIN.

IF YOU PUT THIS DROP ON, YOU SEE,

THE STONE IS LIKE A SPONGE.

DURING THE RAIN, THE WATER GOES INTO THE PORES OF THE STONE,

AND WHEN THE STONE DRIES,

EVERY MATERIAL THAT WAS IN THE WATER GOES OUT

AND IS STAYING ON THE SURFACE.

Narrator: SOPHIE CAN TREAT SOME OF THE SANDSTONE

WITH A SPECIAL WATERPROOFING CHEMICAL.

ON THIS SURFACE, THERE'S AN HYDROPHOBIC AGENT,

SO WHEN I PUT A WATER DROP, YOU CAN SEE, IT STAYS.

Narrator: BUT SOME STONES CAN BE ROTTEN TO THE CORE

WITH NO VISIBLE SIGNS ON THE OUTSIDE.

*

SO THE TEAM DECIDES TO PROBE THE INSIDE OF THE BUTTRESSES

WITH A SPECIAL DRILL HOOKED UP TO A COMPUTER.

*

SOPHIE'S COLLEAGUE JASPER DRILLS IN TO THE SOFT SANDSTONE.

*

THE COMPUTER MEASURES THE RESISTANCE TO THE DRILL,

REVEALING WEAKNESSES IN THE STONE.

WHAT WILL THE RESULTS TELL US?

*

Narrator: AT THE COLOGNE CATHEDRAL,

A RESTORATION TEAM MUST REPAIR AND REPLACE THIS BUTTRESS.

NOT EVEN STONE LASTS FOREVER.

WE WILL USE SOME CONSOLIDANT AGENT

TO MAKE THE STONE HARD AGAIN,

AND THEN WE TEST WHETHER IT WORKED.

Narrator: SO WHY DID MODERN BUILDERS

USE SUCH POOR-QUALITY STONE?

*

THE PROBLEM WAS THEY COULDN'T FIND ENOUGH GOOD MATERIAL

TO FINISH SUCH AN ENORMOUS TASK.

WHEN THEY STARTED BUILDING,

ALL THAT EXISTED WAS THE BACK END OF THE CHURCH,

THE RUIN OF THE SOUTH TOWER,

AND A HUGE, HALF-FILLED GAP IN THE MIDDLE.

JUST TO GET THIS FAR,

MEDIEVAL BUILDERS HAD RIPPED THE TOP OFF A NEARBY MOUNTAIN.

BUT THIS SOURCE OF STONE RAN DRY.

SO 19th-CENTURY BUILDERS

HAD TO FIND THOUSANDS OF TONS OF SANDSTONE

FROM MANY DIFFERENT SOURCES ALL OVER GERMANY.

HERE, THEY USED THE HIGHEST SCAFFOLD OF THE TIME

TO PLACE THE STONES

AND FINISH THE CATHEDRAL IN JUST 38 YEARS.

SO DID THE BUILDERS SACRIFICE QUALITY

IN THEIR RACE TO FINISH THE CATHEDRAL?

LOCAL LEGEND SAYS

THERE'S SOMETHING NOT QUITE RIGHT ABOUT THE TOWERS.

ARCHITECT DOUG PRITCHARD IS GOING TO USE HIS SCANNER

TO MEASURE JUST HOW TALL THEY REALLY ARE.

Pritchard: THERE IS A CERTAIN MYSTERY

REGARDING THE HEIGHTS OF THE TWO TOWERS.

ARE THEY EXACTLY THE SAME?

IS ONE HIGHER THAN THE OTHER?

AND THAT'S WHAT THE SCANNING WILL CONFIRM.

Narrator: DOUG HITCHES A RIDE

THROUGH THE CORE OF THE NORTH TOWER.

*

Pritchard: WE'RE UP ON THE NORTH TOWER AT THE 100-METER LEVEL,

AND WHAT I'M GOING TO DO IS SET UP THE TRIPOD AND SCANNER INSIDE

SO THAT WE CAN CAPTURE THE ENTIRE INTERIOR OF THE TOWER.

Narrator: THIS IS THE FIRST TIME

THAT ANYONE HAS MEASURED THE TOWERS WITH SUCH ACCURACY.

Pritchard: WHAT I'M ABLE TO DO IS DO A 360-DEGREE SCAN

OF THE ENTIRE INTERIOR OF THE TOWER,

AND THAT WILL GIVE ME SUB-CENTIMETER-LEVEL DATA.

THE SCANNER CAN GENERATE

OVER 1 MILLION DIMENSION POINTS IN A SECOND,

SO WITHIN 15 MINUTES,

WE'RE GONNA HAVE A MASSIVE AMOUNT OF INFORMATION.

Narrator: DOUG PUTS THE SCANNER TO WORK.

*

THE FINAL STONE WAS LAID ON TOP OF THE SOUTH TOWER IN 1880.

CONSTRUCTION HAD LASTED 632 YEARS AND 2 MONTHS.

DOUG MAKES A DISCOVERY THAT ASTONISHES EVEN HIM.

Pritchard: LOOKING AT THE DATA,

COMPARING THE HEIGHT OF THE SOUTH TOWER AND THE NORTH TOWER,

THEY ARE ALMOST EXACTLY THE SAME HEIGHT.

THE SOUTH TOWER IS JUST SLIGHTLY, SLIGHTLY TALLER

THAN THE NORTH --

ONLY BY 4 CENTIMETERS, WHICH IS REALLY REMARKABLE.

ALSO, IF YOU CONSIDER THE AGE OF THE TWO TOWERS,

REALLY TELLS YOU ABOUT THE CRAFTSMANSHIP

AND THE SKILLS OF THE PEOPLE THAT BUILT THIS BUILDING.

Narrator: DOUG'S SCANS ARE A PRECISE,

DIGITAL COPY OF THE CATHEDRAL.

*

THEY REVEAL HOW GENERATIONS OF CRAFTSMEN

REMAINED TRUE TO A DESIGN THAT'S MORE THAN 700 YEARS OLD.

WHEN YOU COMPARE THIS BUILDING WITH CONTEMPORARY BUILDINGS,

WHAT IS TRULY AMAZING HERE IS

THAT EVERYTHING HAS BEEN MADE BY HAND, BY CRAFTSMEN.

EVERYTHING FROM INDIVIDUAL STONES TO THE ENTIRE STRUCTURE,

AND THAT REALLY IS SIGNIFICANT.

IT ISN'T MANUFACTURED OFF SITE.

IT ISN'T COMING OUT OF A FACTORY.

THIS WAS DONE BY HAND.

THE VISION BEHIND IT,

BY THE PEOPLE THAT WANTED THIS BUILT, IS INCREDIBLE.

IT IS A REALLY SIGNIFICANT BUILDING

IN ITS SIZE AND ITS BEAUTY AND ITS GRANDEUR.

*

Narrator: COLOGNE CATHEDRAL, LIKE ITS PREDECESSOR AT AMIENS,

IS AN EXTRAORDINARY ACHIEVEMENT.

*

TODAY, MILLIONS OF PEOPLE PASS THROUGH

THEIR RICHLY-DECORATED DOORS TO GAZE AT THE FIRST SKYSCRAPERS,

WHICH TOOK MANY LIFETIMES TO COMPLETE.

COLOGNE CATHEDRAL CONTINUES

TO INSPIRE AWE AND DEVOTION TODAY...

...THANKS TO ITS SOARING GOTHIC ARCHES,

WHICH REVOLUTIONIZED ARCHITECTURE...

...AND A DAZZLING INTERIOR AWASH WITH SUNLIGHT

FROM THOUSANDS OF SHARDS OF PAINTED GLASS.

COLOGNE'S SHEER SIZE AND COMPLEXITY

CONTINUE TO AMAZE ENGINEERS TODAY.

ITS TWO ICONIC TOWERS STAND OUT LIKE BEACONS...

DRAWING VISITORS FROM ACROSS THE WORLD

TO THIS MEDIEVAL WONDER.