Narrator: MACHU PICCHU,
THE JEWEL OF THE INCA EMPIRE,
BUILT HIGH IN THE ANDES MOUNTAINS
WITHOUT MACHINES OR EVEN THE WHEEL.
THIS IS THE APEX OF INCA DEVELOPMENT AND CONSTRUCTION,
AND PERHAPS OF ANY CIVILIZATION IN THE NEW WORLD.
Narrator: YET FLOODS, EARTHQUAKES, AND LANDSLIDES
RAVAGE THIS REMOTE REGION.
HOW CAN MACHU PICCHU SURVIVE?
TO FIND OUT, WE WILL STRIP THE CITY...
TO REVEAL ITS SECRET INNER WORKINGS...
AND EXPOSE THE INGENIOUS TECHNOLOGY...
THAT ALLOWED ENGINEERS TO BUILD THIS CITY
ON THE BRINK OF DISASTER.
-- Captions by VITAC -- www.vitac.com
CAPTIONS PAID FOR BY DISCOVERY COMMUNICATIONS
MACHU PICCHU,
THE CROWNING GLORY OF THE ANCIENT INCA EMPIRE.
IN 16th-CENTURY PERU,
THIS MOUNTAIN CITY WAS HOME TO 1,000 PEOPLE
LIVING AND WORKING A DIZZYING 8,000 FEET ABOVE SEA LEVEL.
BUILT IN THE ANDES MOUNTAINS,
MACHU PICCHU WAS A VITAL POLITICAL
AND CEREMONIAL CENTER FOR THE INCA.
A MAGNIFICENT SETTLEMENT
OF TEMPLES, WORKSHOPS, AND HOMES.
INCA ENGINEERS BUILT VAST TERRACES INTO THE HILLSIDE
TO HOLD THE MOUNTAIN IN PLACE
AND PROVIDE SPACE FOR CROPS.
THIS ANCIENT CIVILIZATION
CONQUERED THEIR EXTREME ENVIRONMENT,
BUILDING THE CITY THAT WOULD STAND FOR CENTURIES.
EVERY YEAR, A MILLION PEOPLE
JOURNEY TO THIS REMOTE PART OF PERU
TO MARVEL AT THE REMAINS OF THIS ICONIC CITY.
FEW REALIZE THAT IT IS SURROUNDED
BY SOME OF THE MOST TREACHEROUS TERRAIN ON EARTH.
POWERFUL LANDSLIDES TEAR DOWN THE MOUNTAINS.
VIOLENT EARTHQUAKES AND FLOODS
DEVASTATE SETTLEMENTS IN THE VALLEYS.
"MY HOUSE IS GONE.
"I'VE LOST EVERYTHING.
EVERYTHING IS RUINED."
[ CRYING ]
DESPITE THE CRUEL ENVIRONMENT,
MANCHU PICCHU HAS STOOD FIRM FOR OVER 500 YEARS.
TODAY, ARCHEOLOGISTS RACE TO DISCOVER THE SECRETS
OF THIS ANCIENT CITY.
MODERN ENGINEERS CAN ALSO LEARN TECHNIQUES
FROM THE GENIUS OF THE INCAS.
IN THE 1500s,
THE INCA EMPIRE WAS THE LARGEST NATION ON EARTH.
THESE ANCIENT INNOVATORS WORSHIPPED THE SUN
AND USED BOTH POLITICAL PROWESS AND MILITARY MIGHT
TO DOMINATE SOUTH AMERICA.
THEY DIDN'T DEVELOP THE WHEEL OR A WRITTEN LANGUAGE,
BUT THEIR HUGE STONE CITIES CONTINUE TO ASTOUND RESEARCHERS.
Ziegler: I CALL THE INCA THE ROMANS OF THE NEW WORLD.
ENGINEERING IS THEIR GREATEST ACCOMPLISHMENT.
Narrator: GEOLOGIST GARY ZIEGLER
HAS BEEN STUDYING MACHU PICCHU SINCE THE 1960s.
HE IS TRYING TO SOLVE THE MYSTERY
OF HOW THE INCA BUILT MASSIVE WALLS AND BUILDINGS
THAT COULD SURVIVE EARTHQUAKES.
REMARKABLY, THESE GRANITE BLOCKS WERE SHAPED BY HAND
WITHOUT MACHINES OR METAL TOOLS.
I'M LOOKING AT A BIG PIECE OF GRANITE HERE,
AND WE'RE GONNA TRY A DEMONSTRATION
OF HOW WE THINK THE INCA WERE ABLE TO SHAPE THESE ROCKS.
BUT YOU CAN SEE
THAT I'M BEGINNING TO FRACTURE OFF PIECES.
GRANITE, OF COURSE, CONSISTS LARGELY
OF CRYSTALS OF QUARTZ, MICA, AND FELDSPAR.
AND THOSE FRACTURE FAIRLY EASILY.
SO LET'S POUND AWAY HERE AND SEE WHAT WE CAN DO.
IT SEEMS A SLOW PROCESS,
BUT I'M MAKING PRETTY GOOD TIME HERE.
UH-OH.
ALL RIGHT, THIS WOULDN'T BE UP TO INCA STANDARDS.
I'M GONNA HAVE TO SWITCH TO ANOTHER STONE.
Narrator: GRANITE IS ALMOST 10 TIMES STRONGER THAN CONCRETE
AND FRACTURES EASILY, MAKING IT IDEAL FOR BUILDING.
THE INCAS SCULPTED THE BLOCKS BY HAND
TO PACK TOGETHER TIGHTLY.
THERE'S NO CEMENT GLUING THEM IN PLACE.
SO HOW DID THESE WALLS STAY STANDING
IN A COUNTRY HIT BY MORE THAN 100 EARTHQUAKES A YEAR?
TO FIND OUT,
GARY IS VISITING THE CONVENT OF SANTO DOMINGO
IN THE NEARBY CITY OF CUSCO.
IN INCA TIMES, THIS WAS A SACRED SUN TEMPLE,
THE WALLS FINELY CARVED.
WHEN THE SPANISH INVADED IN THE 1530s,
THEY BUILT A CONVENT ON TOP.
WHAT WE SEE HERE -- YOU SEE THE CEMENT MORTAR,
AND THAT'S THE INDICATION
THAT THIS WAS INDEED COLONIAL, NOT INCA.
OF COURSE, IT'S VERY OBVIOUS TO SEE.
THE STONES ARE SIMILAR TO INCA STONES,
BUT THEY WERE CHIPPED OUT PROBABLY WITH A STEEL CHISEL
AND HAMMERED DURING COLONIAL TIMES.
Narrator: THESE 16th-CENTURY WALLS LOOK STRONG,
BUT THEY CANNOT WITHSTAND THE FORCES OF NATURE.
1950 -- A HUGE EARTHQUAKE ROCKS CUSCO,
DEVASTATING OVER HALF THE CITY.
COLONIAL WALLS COME CRASHING DOWN,
BUT THE INCAS' STONEWORK SURVIVES.
YOU CAN SEE THE OBVIOUS DIFFERENCE HERE.
THIS REPRESENTS THE FINEST OF INCA CONSTRUCTION AND STONEWORK.
IN FACT, THE JOINTS ARE SO TIGHT
THAT IT'S IMPOSSIBLE TO PUT A KNIFE BLADE OR A RAZOR BLADE
BETWEEN THEM.
Narrator: AMAZINGLY,
THE LACK OF MORTAR IS THE KEY TO BUILDING QUAKE-PROOF WALLS.
WHEN SPANISH CONQUERORS BUILT A CONVENT
AROUND THE ANCIENT INCA TEMPLE,
THEY USED THICK CEMENT
TO HOLD THE ROUGHLY WORKED BLOCKS TOGETHER.
THIS ALLOWED THEM TO BUILD HIGHER AND QUICKER.
BUT CEMENT CRACKS UNDER PRESSURE,
ESPECIALLY WHEN AN EARTHQUAKE HITS.
INCA WALLS HAVE NO WEAK POINTS.
IN AN EARTHQUAKE,
HUGE FRICTION BETWEEN THE PERFECT SURFACES
STOPS THEM FROM SLIPPING.
THIS HAS KEPT THE INCA WALLS INTACT
THROUGH 500 YEARS OF QUAKES.
Ziegler: YOU CAN IMAGINE ALL OF THIS STUFF SHAKING
AND THEN THE COLONIAL, OR THE MODERN, WALLS
JUST CRUMBLING AROUND
AND LEAVING THE INCA TEMPLES INTACT.
THE INCAS WOULD HAVE SMILED ABOUT THIS.
Narrator: THE TEMPLES OF MACHU PICCHU
HAVE THE SAME QUAKE-PROOF DESIGN.
[ RUMBLING ]
THE STONES FIT TOGETHER PERFECTLY.
BUT THE MOUNTAINTOP LOCATION
GIVES THE BUILDINGS ADDED PROTECTION AGAINST EARTHQUAKES.
THE GRANITE BEDROCK PLUNGES DEEP INTO THE EARTH'S CRUST.
DEEPLY ROOTED,
THE ROCK REMAINS STEADY AS THE SURROUNDING GROUND SHAKES.
IT CAN DEFLECT ANY SHOCK WAVES AWAY FROM THE CITY,
KEEPING THE HOMES INTACT.
IN MODERN-DAY LIMA, THE CAPITAL CITY OF PERU,
ENGINEERS ARE DRAWING INSPIRATION
FROM THEIR ANCIENT PREDECESSOR.
ENGINEER DAVID ARISMENDEZ IS BUILDING A SEVEN-STORY TOWER
AND MUST PROTECT IT FROM EARTHQUAKES.
"THIS IS A SEISMIC ISOLATOR.
"THIS SYSTEM, AS YOU CAN SEE,
"SEPARATES HERE INTO THE BASEMENT LEVEL DOWNWARDS
"AND THE GROUND FLOOR UPWARDS.
"THE BUILDING, AS YOU CAN SEE, ALL THE ACROSS THIS LEVEL,
IS SUPPORTED BY COLUMNS WITH ISOLATORS."
THESE CYLINDERS ACT AS SHOCK ABSORBERS
FOR THE WHOLE BUILDING.
EACH IS MADE OF LAYERS OF RUBBER AND LEAD.
IN AN EARTHQUAKE,
BOTH THESE MATERIALS CAN FLEX
AND THEN RETURN TO THEIR ORIGINAL SHAPE...
...ABSORBING THE FORCE OF THE QUAKE.
THESE ISOLATORS SHOULD KEEP THE TOWER
AS SAFE AS THE WALLS OF MACHU PICCHU.
EARTHQUAKES WERE JUST ONE OF MANY PROBLEMS
THE ANCIENT INCAS CONQUERED.
HIGH IN THE ANDES,
MACHU PICCHU IS ALSO VULNERABLE TO EXTREME WEATHER.
WITH OVER SIX FEET OF ANNUAL RAIN,
HOW DID THEY STOP THE CITY FROM BEING WASHED AWAY?
Narrator: MACHU PICCHU.
THIS BREATHTAKING INCA CITY HAS SURVIVED HUNDREDS OF YEARS
IN THE HEART OF AN EARTHQUAKE ZONE
THANKS TO FLAWLESS STONE MASONRY.
BUT ITS BUILDERS FACED ANOTHER BIG CHALLENGE...
PROVIDING WATER.
CARRYING WATER UP FROM THE RIVER IN THE VALLEY
MEANT AN EXHAUSTING 1,500-FEET CLIMB.
YET THIS ANCIENT CITY THRIVED. HOW?
THE SOLUTION WAS SIMPLE, YET INGENIOUS.
ON THE MOUNTAIN ABOVE MACHU PICCHU,
THE INCAS DISCOVERED A NATURAL SPRING.
THE SPRING FLOWED ALL YEAR 'ROUND,
SO ENGINEERS CHANNELED IT INTO A CANAL 2,400 FEET LONG.
THEY BUILT THE CANAL AT AN ANGLE
SO GRAVITY COULD FEED 47,000 GALLONS OF WATER EVERY DAY
DOWN THROUGH THE CITY INTO 16 FOUNTAINS...
...QUENCHING THE THIRST OF 1,000 CITIZENS
AND KEEPING THEM CLEAN.
THESE FOUNTAINS STILL FLOW TODAY,
BUT THE WATER COMES FROM A HOSE PIPE.
THE CANAL THAT ONCE FED THEM HAS LONG SINCE DRIED UP.
CIVIL ENGINEER DR. CHRISTINE FIORI
IS HUNTING FOR THE ORIGINAL WATER SOURCE.
Fiori: THE CHANNEL'S DEFINITELY THERE.
IT'S JUST COMPLETELY OVERGROWN.
I THINK THIS WOULD HAVE LOOKED A LOT DIFFERENT IN INCA TIMES.
THE SOURCE OF THE WATER WAS VERY PRECIOUS TO THEM,
SO I IMAGINE THAT IT WOULD HAVE BEEN CLEARED
AND KEPT CLEAR TO KEEP THAT WATER FLOWING.
Narrator: THE SECRET TO THE ANCIENT SPRING
LIES IN THE ROCKS TOWERING ABOVE CHRISTINE.
DURING THE WET SEASON,
MORE THAN SIX FEET OF RAIN FALLS ON MACHU PICCHU.
THE WATER SEEPS THROUGH THE EARTH.
THE GRANITE FILTERS OUT ANY IMPURITIES IN THE WATER
BEFORE IT BECOMES TRAPPED IN FRACTURES
THAT CUT THROUGH THE ROCK.
THE WATER FLOWS OUT OF THE MOUNTAINSIDE FORMING A SPRING.
THE ANCIENT INCAS BUILT A STONE TROUGH
TO HARNESS THIS NATURAL RESOURCE
AND CHANNEL WATER TOWARDS THE CITY.
Fiori: THIS WALL RIGHT HERE IS USED TO HOLD BACK THE SOIL
AND KEEP THIS AREA OPEN.
THIS WALL WAS ACTUALLY BUILT TO CONTAIN THE WATER.
THE STRUCTURE THAT THEY BUILT TO CONTAIN IT IS REALLY IMPRESSIVE.
Narrator: AT THE TIME OF THE INCAS,
THE WATER PRESSURE IN THESE FOUNTAINS
WAS FIVE TIMES HIGHER THAN THE AVERAGE U.S. SHOWER
AND CLEAN ENOUGH TO DRINK.
BUT THE ANCIENT ENGINEERS FACED YET ANOTHER PROBLEM.
EVERY NOVEMBER, THE RAINY SEASON HIT.
THE CITY GETS MORE RAIN IN THREE MONTHS
THAN SEATTLE GETS IN A YEAR.
TERRIBLE FLOODS RIP THROUGH THE VALLEYS.
YET MACHU PICCHU REMAINS DRY.
THAT'S BECAUSE ENGINEERS BUILT THE FOUNTAINS
TO OVERFLOW IN HEAVY RAIN.
THEY ALSO CREATED DRAINAGE OUTLETS IN THE WALLS
TO MOVE WATER AWAY FROM VULNERABLE HOMES.
Fiori: IT'S VERY IMPRESSIVE THAT THE INCA UNDERSTOOD
THE WHOLE CONCEPT OF MOVING WATER AWAY
AND THE ENERGY ASSOCIATED WITH WATER
AND WHAT IT COULD DO TO FOUNDATIONS.
Narrator: JUST BELOW THE ANCIENT CITY,
MODERN ENGINEERS ARE HARNESSING MACHU PICCHU'S INTENSE RAINFALL
TO GENERATE HYDROELECTRIC POWER.
LIKE THE INCA CANALS, GRAVITY IS THE KEY.
ENGINEERS DIVERT RIVER WATER THROUGH THE MOUNTAIN
SO IT FALLS 1,200 FEET DOWN THE SLOPE.
PLANT MANAGER ANDY RODRIGUEZ...
MACHU PICCHU.
...AND ENGINEER MARIO SCALETTA MUST REGULARLY INSPECT THE AREA
WHERE WATER ENTERS THE PIPES.
IT'S VERY IMPORTANT TO HAVE A HUGE AMOUNT OF WATER,
BUT IT'S ALSO VERY IMPORTANT TO HAVE A DIFFERENCE IN ELEVATION.
THE MORE FLOW AND THE MORE HEAD YOU HAVE,
THE MORE ENERGY YOU PRODUCE.
Narrator: NOW WORKERS ARE INSTALLING A NEW GENERATOR
AT THE BASE OF THE MOUNTAIN.
POWERED BY THE FALLING WATER,
IT WILL DOUBLE THE PLANT'S OUTPUT...
PROVIDING 350,000 PEOPLE WITH ELECTRICITY.
THE NEW DESIGN ALSO PROTECTS THE STRUCTURE
FROM PERU'S MOST EXTREME WEATHER.
TO SAFEGUARD THE NEW PLANT FROM FLOODS,
MARIO AND ANDY ARE BUILDING IT IN A SEALED BUNKER
200 FEET BELOW GROUND.
BUT THIS FAR DOWN,
THE WATER CANNOT FLOW STRAIGHT BACK INTO THE RIVER,
SO THEY'RE DIGGING TWO NEW TUNNELS.
THESE CAN CHANNEL 16,000 GALLONS OF WATER A SECOND
TO AN OUTLET TWO MILES AWAY...
WHERE THE RIVER IS LOWER.
THE UNDERGROUND PLANT IS SEALED WATERTIGHT.
AND AT THE TOP OF THE HILL,
A UNIQUE SYSTEM DIVERTS FLOODS SHOULD THEY STRIKE.
Scaletta: WE ARE NOW AT THE TOP OF THE HILL,
400 METERS ABOVE THE LEVEL OF THE DIRT BANKS.
ANDY, WHAT IS THE FLOW RATE THAT WE HAVE HERE RIGHT NOW?
[ SPEAKS NATIVE LANGUAGE ]
WE HAVE, RIGHT NOW, 31 CUBIC METERS PER SECOND.
IN THE EVENT OF A FLOOD,
WE SHUT DOWN THESE GATES
SO ALL THAT WATER IS DIVERTED INTO THE URUBAMBA RIVER.
Narrator: THE MACHU PICCHU MOUNTAIN POWER PLANT
IS ONE PART OF A NETWORK
THAT FEEDS CLEAN, RENEWABLE ELECTRICITY
TO MODERN-DAY PERU.
THERE ARE 23 HYDROELECTRIC PLANTS ACROSS THE ANDES.
THEY GENERATE OVER 70% OF THE COUNTRY'S ELECTRICITY...
...POWERING THE HOMES OF MORE THAN 22 MILLION PEOPLE.
LIKE PERU'S MODERN-DAY ENGINEERS,
THE INCAS HARNESSED THE POWER OF WATER
WHILE KEEPING THE CITY SAFE FROM FLOODS.
BUT TO CONTROL THEIR EMPIRE,
THE INCAS NEEDED ROADS AND BRIDGES
THAT COULD SPAN THE ANDES AND CROSS A CONTINENT.
Narrator: MACHU PICCHU, PRIDE OF THE INCA EMPIRE.
AN ANCIENT CIVILIZATION
THAT STRETCHED 2,500 MILES, DOMINATING SOUTH AMERICA.
THE ENGINEERS' GREATEST CHALLENGE --
TRANSPORTING GOODS
ACROSS SOME OF THE STEEPEST PEAKS ON THE PLANET
WITHOUT ANY WHEELED VEHICLES.
A WHEEL IS NOT GONNA DO YOU ANY GOOD IN THIS TERRAIN.
WITH ALL OF THE STEEPNESS AND THE VERTICALITY,
YOU NEED TO CARRY THINGS.
SO THE IDEA OF ACTUALLY BUILDING THE ROAD FOR WALKERS
AND LLAMA CARAVANS WAS WHAT YOU SAW.
Narrator: BUT THESE ARE NO ORDINARY ROADS.
THEIR SECRET LIES HIDDEN BENEATH THE SOIL AND DIRT --
FLAT, GRANITE STONES.
THEY ALLOW WATER TO RUN STRAIGHT OFF THE ROAD,
LEAVING NO PUDDLES TO SLIP IN.
GRANITE WALLS SUPPORT THE ROAD
TO STOP EROSION AND HOLD THE SLOPE IN PLACE.
TO TRAVERSE STEEP CLIFFS,
THEY BUILT STAIRCASES INTO THE MOUNTAINSIDE...
...LINKING TOGETHER MORE THAN 25,000 MILES OF ROAD,
FORMING ONE OF THE MOST ADVANCED HIGHWAY NETWORKS IN THE WORLD.
THE KINGS OF THE ROAD WERE THE CHASQUIS...
AN ELITE TEAM OF RUNNERS
WHO CARRIED MESSAGES FROM TOWN TO TOWN.
Fiori: THE CHASQUIS WERE THE INTERNET OF THE ANCIENT TIMES.
THERE'S A STORY THAT I'VE HEARD THAT THE INCA,
WHEN HE WAS HERE IN MACHU PICCHU,
HE WANTED FRESH FISH FROM THE COAST EVERY DAY.
AND SO THIS SYSTEM OF ROADS ENABLED THE CHASQUIS
TO RUN WITH FRESH FISH AND GET IT TO MACHU PICCHU.
Narrator: THAT'S A DISTANCE OF OVER 350 MILES --
ALL ON FOOT.
ROADS ALLOWED THE INCA TO CONQUER THE ANDES,
BUT THEY FACED YET ANOTHER CHALLENGE --
HOW TO CROSS THE DEEP VALLEYS.
STEEP CLIFFS ARE HARD TO CLIMB,
POWERFUL RIVERS, DANGEROUS TO CROSS.
THE INCAS NEEDED BRIDGES.
BUT HOW DO YOU CROSS CANYONS WITH NO IRON OR STEEL?
LEARNING HOW HER ANCESTORS SOLVED THIS PROBLEM
HAS BECOME A PASSION
FOR PERUVIAN ENGINEER CARMEN ALISPEDAY.
THIS IS MY ANCESTORS' LEGACY
AND THE LAST INCA HANGING BRIDGE OF THE INCAS.
AND, OF COURSE, I FEEL SO HAPPY WHEN I SEE IT.
Narrator: THE INCAS BUILT SOME OF THE FIRST SUSPENSION BRIDGES
SEEN ANYWHERE IN THE WORLD.
AND THE KESHWA CHACA BRIDGE STILL PROVIDES A VITAL LINK
FOR THE COMMUNITIES ON EITHER SIDE OF THIS GORGE.
EVERY YEAR SINCE INCA TIMES,
LOCALS REBUILD THE BRIDGE USING THE ONLY AVAILABLE MATERIAL --
GRASS.
THEY BRING IT FROM UP THE MOUNTAINS,
4,000 METERS HIGH.
WE'RE WEAVING THE FIRST ROPES.
WITHOUT ANY KNOT, IT WILL CONTINUE.
SHE'S AN EXPERT. [ CHUCKLES ]
Narrator: THE TWISTING TECHNIQUE IS THE KEY
TO THE ROPE'S STRENGTH,
ENSURING MAXIMUM FRICTION
BETWEEN THE BLADES OF GRASS.
Alispeday: NO IRON, NO CEMENT,
JUST EXACTLY LIKE THE INCAS TAUGHT THEM.
Narrator: LEGEND HAS IT THESE GRASS BRIDGES WERE SO STRONG,
THE SPANISH INVADERS WERE ABLE TO CARRY THEIR CANNONS ACROSS.
TO INVESTIGATE THE BRIDGES' TRUE STRENGTH,
A SAMPLE OF THE ROPE IS BEING TESTED AT MIT IN BOSTON
BY CIVIL ENGINEER JOHN OCHSENDORF.
ON ONE HAND, YOU THINK TO YOURSELF,
"THE NERVE OF THESE PEOPLE
"TO PROPOSE THAT YOU COULD SPAN SUCH A LONG DISTANCE
"WITH SUCH A SMALL AMOUNT OF MATERIAL
THAT'S OBVIOUSLY VERY WEAK."
AND YET THAT'S A PERFECT EXAMPLE
OF THE INGENUITY OF INCA BUILDERS.
Narrator: JOHN LOADS HIS ROPE SAMPLE INTO THE RIG
TO FIND OUT JUST HOW MANY SPANISH SOLDIERS IT COULD HOLD.
HE TURNS THE HANDLE TO APPLY WEIGHT.
Ochsendorf: RIGHT NOW WE HAVE FIVE POUNDS.
10 POUNDS. 15.
Narrator: TWO SENSORS MONITOR THE FORCE
AND HOW MUCH THE ROPE STRETCHES.
Ochsendorf: A BIT FASTER NOW.
75 POUNDS.
I HEAR CREAKING.
THERE'S SOME OF THE CORD THAT'S SLIPPING,
AND I SEE IT COMING APART,
AND SO, AT THIS POINT,
IT'S REALLY NOT CARRYING ANY LOAD AT ALL,
AND IT'S JUST COMPLETELY COME APART.
BUT AT ITS ULTIMATE STRENGTH,
THIS WAS ABLE TO HOLD ABOUT 80 POUNDS OF FORCE,
WHICH IS NOT BAD FOR SOMETHING MADE OF INDIVIDUAL STRAND.
Narrator: THE THICKEST CABLES IN THE BRIDGE
CAN HOLD AROUND TWO TONS.
TWO TIED TOGETHER WOULD BE ENOUGH TO SUPPORT
A HEAVY BRONZE CANNON,
SUGGESTING THE SPANISH LEGEND IS TRUE.
SPANNING OVER A CANYON WITH SIMPLE GRASS --
THAT'S AN ASTONISHING ACHIEVEMENT,
BUT IT'S ALSO HIGHLY RESOURCEFUL.
Narrator: TODAY, PERU'S FINEST ENGINEERS
ARE DRAWING ON THESE ANCIENT DESIGNS.
THE PUENTE CONTINENTAL
IS THE COUNTRY'S LATEST AND LARGEST SUSPENSION BRIDGE.
STRETCHING 1,700 FEET ACROSS THE RIVER,
IT CONNECTS PERU WITH BRAZIL, FORGING NEW TRADE LINKS.
ENGINEER BIAGIO CAROLO KNOWS THIS BRIDGE BETTER THAN ANY.
HIS COMPANY MAINTAIN IT TO THE HIGHEST STANDARDS.
"THERE IS A LOT OF SIMILARITY BETWEEN THIS BRIDGE,
"IN ENGINEERING TERMS,
"AND THE HANGING BRIDGES THAT THE INCAS MADE IN THE ANDES.
"THEY USE THE SAME PRINCIPLE,
"WHERE ALL THE FORCES THAT ARE GENERATED
"ARE DISTRIBUTED BETWEEN THE EXTREME LEFT
AND THE EXTREME RIGHT."
THE WEIGHT OF THE TRAFFIC IS TRANSFERRED
BY THICK STEEL CABLES
TO CONCRETE ANCHORS ON THE BANKS,
MAKING THIS BRIDGE 3,000 TIMES STRONGER
THAN THE ANCIENT INCA DESIGN.
AND SINCE IT OPENED,
PERU HAS BEEN ABLE TO INCREASE EXPORTS TO BRAZIL BY 500%.
THE INCA LEGACY IS HELPING TODAY'S ENGINEERS
BUILD BIGGER, STRONGER BRIDGES AND BETTER ROADS.
BUT DESPITE THEIR TRANSPORT NETWORK,
THE ANCIENT INCAS HAD NO WAY OF BRINGING IN ENOUGH SUPPLIES
TO SUPPORT THE POPULATION YEAR-ROUND.
ON THIS ISOLATED MOUNTAIN,
INCAN INGENUITY WOULD DECIDE
WHETHER HUNDREDS OF WORKERS SURVIVED OR STARVED.
Narrator: MACHU PICCHU TOWERS 8,000 FEET ABOVE SEA LEVEL.
HAULING SUPPLIES UP THE MOUNTAIN
TO FEED THE 1,000 PEOPLE WHO LIVED HERE WAS IMPOSSIBLE.
THE INCAS HAD TO MAKE
THEIR HIGH-ALTITUDE CITADEL SELF-SUFFICIENT.
FARMING ON SOME OF THE STEEPEST SLOPES IN THE WORLD
IS A FORMIDABLE CHALLENGE.
THE SOLUTION? TERRACES.
MACHU PICCHU IS BUILT INTO HILLS
THAT HAVE GRADIENTS OF UP TO 70%.
TO GROW CROPS HERE,
INCA ENGINEERS CONSTRUCTED TERRACES MADE OF GRANITE ROCK.
A THICK LAYER OF GRAVEL TOPPED WITH SAND AND SOIL
ALLOWED RAIN TO DRAIN AWAY.
THIS GAVE THEM ENOUGH SPACE TO GROW FOUR TONS OF CORN
AND 170 TONS OF POTATOES EVERY YEAR.
THE INCAS KNEW EXACTLY HOW TO ADAPT THE TERRAIN TO GROW FOOD.
THEY ALSO FOUND WAYS OF USING THE LANDSCAPE
TO PRODUCE ANOTHER VALUABLE COMMODITY...
SALT.
THE VILLAGE OF MARAS BOASTS SOME OF
THE MOST IMPRESSIVE SALT PONDS IN THE WORLD --
OVER 3,000 OF THEM.
THE PONDS ARE FED BY SPRING WATER
CONTAINING A VERY HIGH CONCENTRATION OF SALT.
GEOLOGIST GARY ZIEGLER IS INVESTIGATING THEIR SECRETS.
Ziegler: WATER RUNS OUT OF THE SPRING,
AND THERE'S A VERY SOPHISTICATED SYSTEM OF CHANNELS
THAT RUN TO VARIOUS PLACES.
ONCE THE WATER EVAPORATES, WE HAVE ALMOST PURE SALT.
Narrator: BY BECOMING MASTERS OF NATURE,
THE INCA KEPT THEIR 1,000-STRONG WORKFORCE FED AND WATERED.
IN MODERN-DAY PERU,
THERE ARE MORE THAN 30 MILLION MOUTHS TO FEED.
BUT THERE'S A PROBLEM.
ONLY 6% OF THE LAND CAN BE USED FOR FARMING.
MOST OF THE COUNTRY'S FLAT LAND IS ARID DESERT,
WHERE IT'S IMPOSSIBLE TO GROW CROPS.
HOT, MOIST WINDS BLAST THE ANDES MOUNTAINS FROM THE EAST.
AS THE WINDS RISE, THEY COOL.
THIS CAUSES CONDENSATION
AND HUGE AMOUNTS OF RAIN TO FALL.
BY THE TIME THEY REACH THE COAST,
THE WINDS ARE HOT AND DRY.
THIS CREATES A RAIN SHADOW.
MAKING THIS BARREN LAND SUITABLE FOR FARMING
NEEDS A MONUMENTAL SOLUTION,
LIKE DIVERTING AN ENTIRE RIVER.
700 MILES NORTH OF MACHU PICCHU,
ENGINEERS AT THE OLMOS IRRIGATION PROJECT
ARE DOING JUST THAT.
THEIR CHALLENGE --
REDIRECTING THE HUANCABAMBA RIVER
FROM ONE SIDE OF THE ANDES TO THE OTHER.
IT'S A HERCULEAN FEAT.
THEY ARE BUILDING A 140-FEET-HIGH DAM WALL
RIGHT IN THE MIDDLE OF THE RIVER.
THIS CREATES A HUGE RESERVOIR.
THEY'RE CHANNELING THE WATER INTO A 17-FOOT-WIDE TUNNEL
DUG MORE THAN A MILE BELOW THE ANDES.
IT'S THE SECOND DEEPEST TUNNEL IN THE WORLD.
THE FORCE OF THE FALLING WATER WILL TURN TWO HUGE TURBINES,
GENERATING 4,000 GIGAWATTS OF POWER.
WHEN THE WATER REACHES THE DESERT,
IT WILL TRAVEL THROUGH A NETWORK OF PIPES
TO NOURISH 110,000 ACRES OF DRY LAND.
ENGINEER ALFONSO PENIGOS AND HIS TEAM
MUST EXCAVATE 600 FEET OF NEW TUNNELS EVERY MONTH.
THEY USE A TRADITIONAL TECHNIQUE --
DYNAMITE -- TO BLAST THROUGH THE TOUGH GRANITE.
A TUNNEL ALWAYS IS A VERY CHALLENGING JOB.
THE GOOD THING IS THAT THE GUYS HAVE VERY GOOD EXPERIENCE
IN THESE KINDS OF JOBS.
IN A LITTLE BIT,
WE'RE GONNA BE DETONATING THESE EXPLOSIVES
IN ORDER TO ADVANCE ABOUT THREE METERS.
Narrator: WITH THE EXPLOSIVES SET,
THEY LIGHT THE FUSE...
...AND MAKE A RUN FOR IT.
ANOTHER BLAST -- TWO MINUTES.
[ MUFFLED EXPLOSION ]
OH, IT WAS TWO SECONDS, ACTUALLY.
TWO SECONDS.
Narrator: IT WILL TAKE EIGHT YEARS
FOR ALFONSO'S TEAM TO COMPLETE THEIR WORK.
JUST LIKE THE TERRACES OF THEIR INCA ANCESTORS,
THE OLMOS PROJECT IS ALLOWING PERUVIANS
TO TRANSFORM THEIR MOST EXTREME ENVIRONMENTS.
THE INCAS USED INNOVATIVE ENGINEERING
AND SOPHISTICATED PLUMBING TO CONQUER THE ANDES TERRAIN.
CORN AND POTATOES PROVIDED FOOD,
WHILE MEDICINAL CROPS, LIKE COCA,
TREATED THE EFFECTS OF HIGH ALTITUDE.
THEY BUILT STORE HOUSES,
STOCKING THEM HIGH WITH SURPLUS SUPPLIES
TO HELP FEED 12 MILLION PEOPLE ACROSS THE EMPIRE.
BUILDING A CITY THAT CLINGS TO A MOUNTAIN EDGE IS INGENIOUS.
BUT THE TERRAIN POSES AN ADDITIONAL DANGER
THAT CAN WIPE WHOLE TOWNS OFF THE MAP --
LANDSLIDES.
Narrator: THE INCAS WERE MASTERS OF THEIR ENVIRONMENT.
BUT THE MOUNTAIN CITY OF MACHU PICCHU
ISN'T SAFE FROM THE ANDES' BIGGEST THREAT --
LANDSLIDES.
HEAVY RAIN AND FREQUENT EARTHQUAKES
MAKES THE SOIL ON THESE STEEP SLOPE EXTREMELY UNSTABLE.
[ SHOUTING IN NATIVE LANGUAGE ]
NOWHERE IS SAFE FROM THESE DEADLY FORCES.
THIS IS SAKSAYWAMAN --
A MILITARY FORTRESS BUILT BY THE INCAS AROUND 1400 A.D.,
LOCATED 50 MILES FROM MACHU PICCHU,
ITS WALLS TOWER 20 FEET HIGH.
THE GIANT LIMESTONE BLOCKS ARE PERFECTLY CARVED,
BUT THE EARTH BEHIND THEM POSES A HUGE THREAT.
RAINWATER SEEPS THROUGH LAYERS OF SANDY SOIL AND CLAY,
BUT CANNOT PASS THROUGH THE LIMESTONE BEDROCK,
SATURATING THE EARTH ABOVE.
THIS SOIL SLIDES,
PUSHING AGAINST THE ANCIENT WALLS
AND CAUSING THEM TO COLLAPSE.
CHRISTINE FIORI AND GEOLOGIST JOSE CARLOS RAMIREZ PRADO
ARE INVESTIGATING WHICH WALLS ARE MOST AT RISK OF COLLAPSE.
THEY ARE USING A CLEVER TECHNIQUE
CALLED ELECTRO-RESISTIVITY TESTING
TO DISCOVER WHAT TYPE OF SOIL LIES BEHIND THE WALLS.
"THE PROBES ON THAT SIDE
"WILL INTRODUCE ELECTRICITY INTO THE SOIL,
AND THESE ONES IN THE CENTER WILL RECEIVE THE SIGNAL."
THE LONGER THE ELECTRICITY TAKES TO PASS THROUGH THE SOIL,
THE MORE LIKELY IT IS TO RETAIN WATER AND CAUSE A LANDSLIDE.
[ MACHINE BEEPS ]
[ SPEAKS NATIVE LANGUAGE ]
"THE READING SAYS 128.5 OHMS.
SO THIS IS A TYPE OF CLAY-SAND SOIL."
Fiori: WHAT THAT ULTIMATELY MEANS FOR THE WALL SYSTEM
IS WATER IS NOT GOING TO BE ABLE TO DRAIN.
IT'S GONNA BUILD UP BEHIND THE WALL,
POTENTIALLY CAUSING SMALL SOIL CREEPING
OR POTENTIALLY LANDSLIDES,
WHICH COULD ULTIMATELY UNDERMINE THE ENTIRE WALL SYSTEM.
Narrator: ANCIENT MONUMENTS AREN'T THE ONLY THINGS AT RISK.
DEADLY LANDSLIDES OFTEN STRIKE WITHOUT WARNING,
PUTTING WHOLE COMMUNITIES IN DANGER.
DURING THE WET SEASON,
TORRENTIAL RAIN FALLS ON THE HILLS.
IT SATURATES THE SOIL,
WHICH BECOMES UNSTABLE ON THE STEEP SLOPES.
THE SMALLEST EARTH TREMOR
CAN THEN TRIGGER A LANDSLIDE,
CAUSING TONS OF ROCK AND MUD TO RIP DOWN THE MOUNTAIN
AT SPEEDS OF 100 MILES PER HOUR.
[ INDISTINCT SHOUTING ]
IN 2010,
44 SEPARATE LANDSLIDES BLOCKED THE MACHU PICCHU RAILROAD --
THE ONLY ROUTE IN AND OUT OF THE CITY.
1,400 PEOPLE NEEDED AIRLIFTED TO SAFETY.
TODAY, THE WRECKAGE MAY BE CLEARED,
BUT THE LAND COULD EASILY SLIDE AGAIN.
THOUSANDS OF PEOPLE USE THE LINE EACH DAY,
UNAWARE OF THE DANGER ABOVE THEM.
GEOLOGIST GARY ZIEGLER IS INVESTIGATING
WHICH PARTS OF THE TRACK ARE MOST AT RISK.
HE'S JOINED BY LANDSLIDE EXPERT CARLOS FERNANDEZ BACAVADAL.
[ TRAIN HORN BLOWS ]
THE PULLMAN STARTS BY THE CURTAIN OF THE HILL
TO CONSERVE THE RAILROADS.
THAT MAKES WEAKER THE LOWER PART OF THE SLOPES.
SO IT'S A CONSTANT FIGHT ONCE IT STARTS SLIDING
AFTER IT'S BEEN CUT BY THE CONSTRUCTION.
YES. ONCE IN A WHILE,
TENSION CRACKS START TO APPEAR IN THE UPPER PARTS.
AND THEN THE PROBLEM BEGINS
BECAUSE WATER FILLS THOSE CRACKS.
TO TEST THE STABILITY OF THE EARTH,
CARLOS AND GARY ALSO PLACE SENSORS IN THE GROUND.
BUT THESE SENSORS, CALLED GEOPHONES,
DETECT SOUND WAVES RATHER THAN ELECTRICITY.
ALL THEY NEED TO GENERATE THE INITIAL SOUND PULSE
IS A GOOD THUMP.
16 MILLISECONDS.
IT SEEMS THAT HERE WE HAVE VERY SOFT SOIL.
AND THAT MIGHT BE A LITTLE BIT DANGEROUS
FOR THE SLOPE THAT WE HAVE BEHIND.
IF WE WANT TO BE SURE
THAT THE RAILROADS IN THIS AREA WILL NOT BE AFFECTED,
WE'LL HAVE TO REPEAT OUR TESTING MANY TIMES UPHILL.
MACHU PICCHU HAS ALWAYS SURVIVED LANDSLIDES,
BUT NOW RESEARCHERS ARE DISCOVERING
THAT EROSION FAR BELOW THE ANCIENT CITY MAY POSE A THREAT.
THE URUBAMBA RIVER AT THE BASE OF MACHU PICCHU
IS EXTREMELY POWERFUL.
IT'S GRADUALLY WASHING AWAY THE FOOT OF THE SLOPE
THAT HOLDS UP THE CITY.
ONE MEGA-FLOOD COULD THEN TRIGGER A MASSIVE LANDSLIDE...
...AND BRING THIS ANCIENT CITY CRASHING DOWN.
Narrator: 2010 --
LANDSLIDES DEVASTATE THE TOWNS AND VILLAGES
AROUND MACHU PICCHU.
[ CRYING ]
Narrator: TONS OF EARTH AND MUD CRASHED DOWN THE MOUNTAIN,
FLATTENING HOMES AND SEVERING TRAIN LINES.
MORE LANDSLIDES ARE INEVITABLE,
SO ENGINEERS MUST ASSESS JUST HOW SAFE MACHU PICCHU REALLY IS.
FERNANDO ASTETE IS THE SITE DIRECTOR
RESPONSIBLE FOR THE SAFETY
OF THE 2,500 PEOPLE VISITING THE CITY EVERY DAY.
"PUT THE RULER IN HERE, AND NOW THERE."
FERNANDO'S TEAM HAVE DRILLED HUNDREDS OF TINY METAL MARKERS
INTO THE STONES ALL OVER MACHU PICCHU.
FEW TOURISTS NOTICE THEM,
BUT FOR FERNANDO AND HIS TEAM, THEY'RE VITAL.
"WE TAKE THESE MEASUREMENTS
"TO SEE IF THE STONE BLOCKS ARE MOVING.
"IF THERE WERE PROBLEMS, THE POINTS WOULDN'T MATCH UP.
"THIS IS FUNDAMENTAL.
"WE'D KNOW, 'OH, SOMETHING HAS HAPPENED.'
2.6 MILLIMETERS. YES, IT IS INSIDE THE LIMITS."
FERNANDO'S TEAM HAVE YET TO DETECT A LANDSLIDE.
THAT'S BECAUSE THE INCAS WERE ONE STEP AHEAD
AND KNEW EXACTLY HOW TO SAFEGUARD THEIR CITY.
THE SAME ENGINEERING THAT ALLOWED THEM TO GROW THEIR FOOD
ALSO STOPS THEIR MIGHTY GRANITE BUILDINGS
FROM SLIDING DOWN THE SLOPE.
TERRACES.
THE TERRACES ACT AS HUGE-SCALE MOUNTAIN STABILIZERS.
THEIR DESIGN IS INGENIOUS.
INCA ENGINEERS BUILT 4-FOOT-HIGH WALLS OUT OF GRANITE.
BEHIND THEM,
THEY PLACED LOOSE GRAVEL WITH SAND AND SOIL ON TOP.
THE WALLS ARE BUILT AT AN ANGLE OF PRECISELY FIVE DEGREES,
COMPACTING THE SOIL AND ROCKS
AND KEEPING MILES OF MOUNTAIN SAFE FROM LANDSLIDES.
NEAR CUSCO,
ENGINEERS ARE BUILDING A MODERN VERSION
OF INCA TERRACES
TO PROTECT THE ROADS, RIVERS, AND RAILROAD BELOW.
THEY FILL STEEL CAGES CALLED GABIONS
WITH ROCKS TO REINFORCE THE HILLSIDES.
THIS KIND OF WORKS OFF THE SAME PRINCIPLE
OF STOPPING A BIG TRUCK WITH A SMALL ROCK.
YOU JUST PUT THE SMALL ROCK BEHIND THE WHEEL,
AND THAT WILL AVOID HUNDREDS OF STONES TO GO DOWNHILL.
THE SAME EFFECT WE PRODUCE TO THE SLOPE.
Narrator: THIS MODERN VERSION OF INCA ENGINEERING
WILL ENSURE THESE CLIFFS STAND AS LONG AS MACHU PICCHU.
MACHU PICCHU IS A MIRACLE OF ENGINEERING.
THE ANCIENT PEOPLE WHO BUILT THIS MOUNTAIN CITY
WERE YEARS AHEAD OF THEIR TIME,
ERECTING STRUCTURES THAT CAN SURVIVE EARTHQUAKES,
LANDSLIDES, AND FLOODS.
TODAY, ENGINEERS ARE BORROWING TECHNIQUES
TO SAFEGUARD MODERN PERU
AGAINST WHATEVER THE ANDES CAN THROW AT IT.