Narrator: VENICE.
A CITY UNDER ATTACK FROM THE SEA.
BUILT AT SEA LEVEL,
THE CITY IS NOW SINKING BENEATH THE WAVES.
THIS BEAUTIFUL CITY IS CONSTANTLY FIGHTING NATURE.
AND, AT THE MOMENT, NATURE IS WINNING.
Narrator: SOME PARTS OF VENICE FLOOD 250 TIMES A YEAR.
AND EVERY DECADE, THE CITY SINKS ALMOST AN INCH INTO THE LAGOON.
HOW CAN VENICE 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.
VENICE. LA SERENISSIMA.
THE MOST SERENE.
EVERY YEAR, 16 MILLION VISITORS ARRIVE
TO MARVEL AT ITS ARCHITECTURAL WONDERS
AND GRAND CANALS.
BOATS ARE THE ONLY TRAFFIC IN THIS ISLAND CITY.
SIGHTSEERS,
COMMUTERS,
DELIVERIES,
EVEN THE EMERGENCY SERVICES.
EVERYONE AND EVERYTHING TRAVELS BY WATER.
VENICE SITS IN A HUGE SALTWATER LAGOON
ON THE EDGE OF THE ADRIATIC SEA.
AND, IT'S A CITY UNDER SIEGE.
SALTWATER NOW FLOODS HALF OF VENICE MOST YEARS,
CAUSING MILLIONS OF DOLLARS OF DAMAGE.
THEY CALL THESE FLOODS ACQUA ALTA OR HIGH WATER.
GEOLOGISTS LIKE GUIDO GIORDANO
KNOW THAT WITH SEA LEVELS RISING,
VENICE IS LIVING ON BORROWED TIME.
VENICE GETS FLOODED NOT SIMPLY FROM THE CANALS,
BUT ALSO FROM THE GROUND, WHEN THE WATER RISES.
AS THE FLOODING IS BECOMING MORE AND MORE FREQUENT,
THE CITY IS IN REAL DANGER OF BECOMING A MODERN-DAY ATLANTIS.
Narrator: TODAY, ENGINEERS RACE TO REPAIR VENICE'S SINKING BUILDINGS.
THEY ARE ALSO CONSTRUCTING AN EXTRAORDINARY NEW FLOOD BARRIER
TO PROTECT THE CITY.
BUT IT'S ABOUT MORE THAN KEEPING VENICE SAFE
FOR ITS INHABITANTS.
THEY MUST ALSO PRESERVE SOME OF THE MOST IMPORTANT
HISTORIC BUILDINGS IN THE WORLD.
THE BYZANTINE BASILICA IN ST. MARK'S SQUARE.
THE CHURCH OF GOLD.
ERECTED IN 1063, THEN ADDED TO OVER TIME,
IT'S ONE OF THE MOST DAZZLING BUILDINGS IN VENICE.
THE VENETIANS PILLAGED MARBLE FROM THE EAST,
ADDING IT TO THE BASILICA
OVER 100 YEARS AFTER THE CHURCH WAS ORIGINALLY BUILT.
THE BASILICA'S 60-FOOT-TALL CUPOLAS,
BUILT IN THE 13th CENTURY, ENRICH ITS IMPOSING PROFILE.
ITS DECORATION PROCLAIMS THE STATUS AND GLORY
OF THE ANCIENT VENETIAN REPUBLIC.
BUT TODAY, ITS GRANDEUR IS AT RISK
OF BEING DESTROYED BY THE DEVASTATING FLOODS.
TO TACKLE THE CITY'S PROBLEMS,
ENGINEERS NEED TO UNDERSTAND THEIR CAUSES.
GUIDO GIORDANO THINKS THE ANSWER LIES IN THE LAND BENEATH VENICE.
ISLANDS IN THE LAGOON PROVIDE A CLUE.
Giordano: THIS IS A SALT MARSH.
IT SHOWS US THE KIND OF ENVIRONMENT THAT EXISTED
BEFORE VENICE WAS ACTUALLY BUILT.
NOW, HAVE A LOOK IN HERE.
WE FIND THAT THIS ISLAND IS MADE OF WET AND VERY SOFT SEDIMENT.
THIS SEDIMENT HAS BEEN DEPOSITED OVER MILLENNIA BY RIVERS.
THEY NATURALLY COMPACT AND SINK.
Narrator: THE SOFT SEDIMENT UNDERNEATH THE CITY
IS COMPRESSING UNDER ITS OWN WEIGHT.
BUT THERE IS ANOTHER FACTOR AT WORK HERE, TOO.
VENICE IS PART OF A MUCH BROADER GEOLOGICAL CONTEXT,
WHERE IT IS THE ENTIRE EARTH CRUST THAT IS SINKING.
Narrator: THE ISLAND OF VENICE
SITS TWO MILES OFF THE COAST OF ITALY.
A HUGE GEOLOGICAL TEAR
RIPS RIGHT DOWN THE COUNTRY'S SPINE,
WHERE TWO TECTONIC PLATES, THE EUROPEAN AND THE ADRIATIC, MEET.
BOTH PLATES ARE SLOWLY MOVING.
AS THEY SHIFT,
THE ADRIATIC PLATE, WITH VENICE ON IT,
IS PULLED DOWN UNDER ITALY.
THESE FORCES ARE ONE OF THE MAIN REASONS
THAT VENICE IS CONSTANTLY SINKING.
THESE ARE MASSIVE GEOLOGICAL FORCES THAT WE CANNOT STOP.
SO, THE VENETIAN PEOPLE
JUST HAVE TO FIND A WAY TO LIVE WITH THEM.
Narrator: THE FIRST STEP TOWARDS SAVING VENICE
IS TO WORK OUT EXACTLY HOW FAST IT IS SINKING.
ONE TOOL THAT GEOLOGISTS USE, HISTORIC PAINTINGS.
Giordano: IN THIS PAINTING BY BELLOTTO,
YOU CAN RECOGNIZE THE STAINED, DARK ROCKS,
WHICH TELL THE HIGH-TIDE LEVEL
AT THE TIME OF BELLOTTO IN THE 18th CENTURY.
IF WE LOOK THERE, WE SEE THE ALGAE.
THIS IS THE PRESENT-DAY LEVEL OF THE HIGH TIDE.
IN THE PAINTING, THE HIGH-TIDE LEVEL
WAS ACTUALLY TWO ROWS OF STONES BELOW THE PRESENT LEVEL.
ONE ROW OF STONES IS SOMETHING ABOUT 40 CENTIMETERS THICK.
SINCE TWO LAYERS HAVE BEEN COVERED,
THAT'S ABOUT 80 CENTIMETERS OF SUBSIDENCE
SINCE THE 18th CENTURY.
Narrator: EVIDENCE LIKE THIS REVEALS THAT PARTS OF VENICE TODAY
ARE AROUND TWO AND A HALF FEET LOWER IN THE WATER
THAN IN BELLOTTO'S DAY.
AND THE CITY IS STILL SINKING, ALMOST AN INCH EVERY DECADE.
AS THE CITY SINKS, VENICE'S BUILDINGS FACE A GROWING THREAT.
THE SOFT SOIL BENEATH THEM COULD TRIGGER A COLLAPSE.
VENICE'S BELL TOWERS ARE MOST AT RISK.
THEY TILT BY UP TO SIX FEET.
HOW MUCH LONGER WILL THEY STAND?
GIORGIO MACCHI IS ITALY'S
LEADING ENGINEERING TROUBLESHOOTER.
HE'S HELPED SAVE SOME OF ITALY'S MOST FAMOUS MONUMENTS,
INCLUDING THE LEANING TOWER OF PISA.
IN 1902, THE FAMOUS CAMPANILE IN ST. MARK'S SQUARE COLLAPSED,
ALL 14,000 TONS OF IT.
AMAZINGLY, ONLY THE CARETAKER'S CAT DIED.
ENGINEERS REBUILT THE TOWER.
BUT IT'S BEEN CRACKING EVER SINCE.
THE LARGE CRACKS THAT RIDDLE THE TOWER'S WATERLOGGED FOUNDATIONS
ARE A MUCH GREATER THREAT.
THE FOUNDATIONS OF THE NEW TOWER
ARE TWICE THE SIZE OF THE OLD ONES,
BUT FAR TOO SHALLOW.
AS THE TOWER SLOWLY SINKS INTO THE SOFT SOIL,
ITS FOUNDATIONS ARE BENDING.
TO SAVE THE TOWER,
GIORGIO'S TEAM BRACE ITS FOUNDATIONS
WITH STRAPS TO SQUEEZE THEM TOGETHER.
FIRST, HIS TEAM DIG CHAMBERS AT EACH CORNER OF THE BELL TOWER
TO ACCESS THE FOUNDATIONS.
THEY WRAP TWO HUGE METAL BELTS AROUND THE TOWER'S BASE.
MADE FROM TITANIUM, THEY WON'T RUST IN THE WATERLOGGED GROUND.
THEY INSTALL HUGE BLOCKS OF GRANITE WEIGHING OVER A TON
TO ANCHOR THE BELTS TO EACH CORNER,
HOLDING THE FOUNDATIONS IN A RIGID EMBRACE,
HALTING THE CRACKING.
OVER 100 SENSORS CONSTANTLY MONITOR THE BELTS AND TOWER.
ANY MOVEMENT IS MEASURED TO THE THOUSANDTH OF AN INCH,
GUARDING AGAINST FURTHER DAMAGE.
Macchi: MOST OF THE CRACKS RESPONDED PERFECTLY.
I AM VERY HAPPY WITH THAT.
Narrator: THAT'S ONE BUILDING RESCUED.
BUT ST. MARK'S SQUARE IS ONE OF THE LOWEST POINTS IN VENICE,
WHICH MAKES IT ONE OF THE MOST VULNERABLE SECTIONS OF THE CITY.
TO PROTECT THE SQUARE FURTHER,
ENGINEERS PLAN TO INSTALL MORE UNDERGROUND DEFENSES.
AN INGENIOUS, ONE-WAY DRAINAGE SYSTEM
WHICH WOULD PREVENT WATER RISING UP,
AS WELL AS ALLOWING WATER TO DRAIN AWAY FROM THE SQUARE.
INNOVATIONS LIKE THIS
ARE HELPING TO SAVE VENICE'S BUILDINGS
FROM THE HARSH WATERS OF THE LAGOON.
BUT BUILDINGS ARE JUST ONE ELEMENT OF THE CITYSCAPE.
VENICE'S 400 BRIDGES ARE ALSO UNDER ATTACK.
Narrator: VENICE IS A CITY OF WATER.
HUNDREDS OF BRIDGES LINK THE CITY TOGETHER.
THIS IS THE MOST ICONIC -- THE RIALTO.
BUILT 400 YEARS AGO,
THIS BRIDGE WAS ONCE KNOWN AS THE EIGHTH WONDER OF THE WORLD.
FOR CENTURIES, IT WAS THE ONLY WAY
TO CROSS THE GRAND CANAL ON FOOT.
THE RIALTO IS ONE OF 400 BRIDGES THAT LINK TOGETHER VENICE,
WHICH OTHERWISE WOULD BE JUST A SERIES OF UNCONNECTED ISLANDS.
Narrator: VENICE'S BRIDGES ARE MORE THAN PEDESTRIAN WALKWAYS.
HIDDEN INSIDE THE RIALTO BRIDGE
IS A REMARKABLE EXAMPLE OF THE SECRET ENGINEERING
BEHIND THIS AQUATIC CITY.
THE BRIDGE HAS A DOUBLE PURPOSE.
IT ALSO CARRIES POWER CABLES, DRINKING WATER AND GAS PIPES.
PROPPING THE BRIDGE UP,
HIDDEN UNDER THE STONE AND TIMBER
IS A FOREST OF MORE THAN 12,000 ANCIENT TREE TRUNKS.
THEY BURROW 10 FEET DOWN INTO THE LAYER OF FIRM CLAY.
THE 400-YEAR-OLD POSTS SUPPORT MORE THAN 10,000 TONS OF WEIGHT.
WOODEN POSTS LIKE THESE ARE FOUND ALL OVER THE CITY.
VENICE'S BUILDINGS STAND ON MORE THAN 10 MILLION TREE TRUNKS
THAT WERE HARVESTED ON THE MAINLAND HUNDREDS OF YEARS AGO.
A VAST FOREST SUBMERGED IN WATERLOGGED GROUND
KEEPS THE STRUCTURES FROM SINKING INTO THE MUD.
Giordano: WELL, THESE BEAUTIFUL BUILDINGS AND ARCHITECTURE
IS ACTUALLY FOUNDED ON THE WOODEN POLES.
ONE MIGHT WONDER WHY THE WOOD DOESN'T ROT.
AND THE REASON IS, BECAUSE THESE POLES
ARE ACTUALLY SITTING INSIDE THE UNDERGROUND MUD,
WHICH PROTECTS THEM.
Narrator: HIDDEN IN THE MUD AWAY FROM OXYGEN,
THE PILES ARE SAFE FROM DECAY.
BUT THE STONEWORK THAT ENCASES THEM
IS NOW UNDER ATTACK FROM A SURPRISING NEW SOURCE.
IN THE PAST, PEOPLE IN VENICE USED TO TRAVEL ONLY BY GONDOLA,
WHICH IS A SLOW AND VERY LOW-IMPACT BOAT.
BUT TODAY, MODERN BOATS CAN REALLY DAMAGE
THE FOUNDATION OF BUILDINGS AND BRIDGES.
Narrator: ALL BOATS CREATE A WAKE.
AND IN VENICE, THAT'S A PROBLEM.
THERE'S NO SPACE IN THE CANALS FOR WAVES TO DISPERSE.
THE BANKS CHANNEL CURRENTS DIRECTLY INTO THE FOUNDATIONS.
THE FORCE OF THE WATER EATS INTO THE STONEWORK,
PULLING MORTAR AWAY.
WATER THEN PENETRATES THROUGH THESE CRACKS,
FORMING CAVITIES IN THE MATERIAL AND MUD.
IN THE MOST SEVERE CASES,
THE WOODEN POLES CAN BE EXPOSED TO EROSION,
DESTABILIZING THE BRIDGE.
TODAY, A TEAM OF DIVERS IS INSPECTING THE RIALTO BRIDGE
FOR THE FIRST TIME SINCE IT WAS BUILT OVER FOUR CENTURIES AGO.
THEIR WORK SHOULD REVEAL THE TOLL
THAT TIME, THE TIDES AND MOTORBOATS HAVE TAKEN
ON THE BRIDGE.
[ SPEAKING ITALIAN ]
Zanetti: THIS IS A VERY DIFFICULT SITE.
WE MUST USE BARRIERS BECAUSE OF THE TRAFFIC.
THE WATER TRAFFIC IS VERY, VERY HEAVY.
BEFORE WE CAN SEE THE DAMAGE,
WE HAVE TO CLEAN THE STONES WITH BRUSHES
TO SEE THE CONDITION UNDERWATER OF RIALTO BRIDGE.
Narrator: THE DIVERS RECORD THE CONDITIONS OF THE STONEWORK WITH A CAMERA,
MEASURING ANY DAMAGE THEY FIND.
Zanetti: TODAY, WE HAVE FOUND SOME ANOMALY,
A GAP BETWEEN THE STONE ABOUT 40 CENTIMETER IN SIZE.
Narrator: THEY DISCOVER HOLES UP TO 16 INCHES DEEP
CAUSED BY THE CURRENTS IN THE WATER.
THE DAMAGE COULD GET WORSE IF IT'S NOT REPAIRED,
THREATENING THE FOUNDATIONS
OF VENICE'S OLDEST AND BUSIEST BRIDGE.
PAOLO'S TEAM MUST CONSULT WITH THE CITY OF VENICE
TO FORMULATE A REPAIR PLAN.
ONE SOLUTION --
INJECT WATERPROOF MORTAR INTO THE HOLES.
IT'S A FAMILIAR TECHNIQUE IN VENICE
THAT PREVENTS EROSION FROM UNDERMINING
THE BRIDGE'S SUPPORTS SO THIS VITAL LIFELINE CAN STAY INTACT.
Zanetti: WITH THE UNDERWATER SPECIAL SEALANT,
THE WATER CANNOT GO INSIDE ANY MORE.
I THINK RIALTO BRIDGE
WILL SURVIVE FOR MANY, MANY CENTURIES.
IT'S INGENIOUS ENGINEERING LIKE THIS
THAT PROTECTS VENICE'S HISTORIC BUILDINGS AND BRIDGES
FROM THE WATER.
BUT MORE CHALLENGES REMAIN.
THE CITY IS BEING ATTACKED BY ANOTHER MENACE
THAT ITS EATING ITS BUILDINGS AWAY.
Narrator: BUILDINGS IN VENICE ARE UNDER ATTACK.
THEY ARE BEING ERODED BY THE SALT IN THE SEAWATER.
SALT HAS ALWAYS BEEN A PROBLEM FOR VENETIANS.
IT ATTACKS THEIR BUILDINGS.
AND IT'S IMPOSSIBLE TO DRINK.
VENICE'S SQUARES CONTAIN
HUNDREDS OF LARGE, CIRCULAR STONE OBJECTS.
FEW VISITORS REALIZE THE INCREDIBLE ENGINEERING
LYING JUST BENEATH THEM.
THESE STRUCTURES ARE WELLHEADS.
UNDER THEM ARE NO ORDINARY WELLS.
MOST PLACES IN THE WORLD, YOU DIG A WELL INTO THE GROUND.
THEN YOU CAN DIP IN A BUCKET, GET DRINKING WATER.
NOT HERE IN VENICE. HERE, GROUNDWATER IS SALTWATER.
AND THIS WELL IS VENICE'S ANSWER TO THAT PROBLEM.
Narrator: A LARGE CHAMBER BUILT BY EARLY VENETIANS TO STORE WATER
SITS DIRECTLY BENEATH THE WELLHEAD.
COLLECTORS IN THE SQUARE DIRECT RAINWATER
DOWN INTO A LAYER OF SAND.
THE SAND ACTS AS A NATURAL FILTER,
MAKING THE RAINWATER CLEAN TO DRINK.
A CLAY LINING AROUND THE CHAMBER
PREVENTS THE FRESH WATER FROM ESCAPING
AND ALSO STOPS SALTY GROUNDWATER FROM SEEPING INTO THE CISTERN.
MORE THAN 6,000 WELLS LIKE THIS GAVE VENETIANS INSTANT ACCESS
TO DRINKING WATER ALL ACROSS THE CITY.
WITHOUT SYSTEMS LIKE THIS, THEY COULD NEVER HAVE SURVIVED
IN SUCH A CHALLENGING ENVIRONMENT.
THE SALTY WATER IN THE CANALS AND RISING UP THROUGH THE GROUND
ALSO CAUSES HUGE PROBLEMS FOR THE CITY'S BUILDINGS.
HOUSES IN VENICE ARE BUILT WITH BRICKS.
AND THIS IS BECAUSE BRICKS ARE MADE OF CLAY,
WHICH IS VERY EASY MATERIAL TO FIND IN THE LAGOON.
BUT THEY ARE ALSO VERY POROUS.
THEY SUCK A LOT OF WATER INSIDE.
THIS IS SALT WATER.
SO, WHEN THE WATER EVAPORATES,
THEN IT LEAVES BEHIND CRYSTALS OF SALT.
TO PREVENT THIS PROBLEM,
THE VENETIANS USED TO MAKE THE BASE OF THEIR BUILDING
WITH AN IMPERMEABLE ROCK.
Narrator: EARLY ENGINEERS IN VENICE
USED A LAYER OF WATERPROOF LIMESTONE
UNDERNEATH THEIR BUILDINGS.
RISING JUST ABOVE THE WATER LEVEL,
IT STOPPED SALTWATER
FROM SEEPING INTO THE BRICK WALLS AND PLASTER.
BUT TODAY, THE WATER REGULARLY RISES ABOVE THIS BOUNDARY.
Giordano: SO NOW, THE WATER IS ACTUALLY PENETRATING INSIDE THE WALL.
AND YOU CAN SEE UP THERE,
IT REACHES UP TO TWO OR THREE METERS
FROM THE BASE OF THE BUILDING.
AND THIS IS, OF COURSE, CAUSING SERIOUS DAMAGES.
Narrator: SALT ATTACKS STRUCTURES THROUGHOUT THE CITY.
IF UNTREATED, THIS PROBLEM CAN EVEN LEAD TO COLLAPSE.
HERE AT THE SALUTE CHURCH,
RESTORATION SPECIALIST GIOVANNI ALFIè
USES INGENIOUS TECHNOLOGY TO FIGHT SALT DAMAGE.
GIOVANNI'S TEAM IS PULLING UP MORE THAN 4,500 PIECES OF MARBLE
TO REMOVE THE SALT AND RESTORE THE STONEWORK.
Narrator: BEFORE THEY PUT THE MARBLE BACK,
THE TEAM INSTALLS A SERIES OF PROTECTIVE LAYERS
UNDER THE FLOOR TO KEEP THE SALTY WATER AT BAY.
THEY LAY DOWN A PLASTIC MEMBRANE
ABOVE THE CHURCH'S POROUS BRICK BASE
TO KEEP SALTWATER FROM RISING UP.
A METAL GRILLE PROTECTS IT.
ON TOP, THEY INSTALL TWO MILES OF TUBES.
THE TUBES FEED WARM WATER AROUND THE FLOOR, DRYING ANY MOISTURE.
THEY ENCASE THIS UNDER-FLOOR HEATING SYSTEM IN CONCRETE
AND RE-LAY THE RESTORED MARBLE ON TOP.
THIS WAY, THE SALUTE CHURCH SHOULD REMAIN DRY
AND FREE FROM SALT ATTACKS FOR YEARS TO COME.
PUTTING EACH PIECE OF THE PUZZLE BACK IN THE RIGHT SPOT
ISN'T EASY.
Narrator: IT WILL TAKE GIOVANNI TWO MONTHS TO FINISH THE JOB
BEFORE THE SALUTE CAN REOPEN FOR FULL WORSHIP.
ANOTHER PROBLEM SOLVED.
BUT FOR ENGINEERS IN VENICE, THE CHALLENGES KEEP COMING.
THE SEA ATTACKS THE CITY IN YET ANOTHER WAY --
SUPER FLOODS.
Narrator: SALTY WATER FLOODS PARTS OF VENICE
UP TO 250 TIMES A YEAR, WREAKING HAVOC.
AN EXTRAORDINARY FEAT OF ENGINEERING
BUILT TO SAFEGUARD AGAINST SUCH DISASTERS
STANDS 10 MILES OFFSHORE --
A UNIQUE FLOOD- AND WEATHER-MONITORING STATION
CRAMMED WITH INNOVATIVE TECHNOLOGY.
ON BOARD, A WEATHER STATION...
RESEARCH LABORATORY...
AND EQUIPMENT THAT MEASURES SEA LEVELS.
IT TOWERS 50 FEET ABOVE THE WATER.
FOUR STEEL LEGS ANCHORED 72 FEET INTO THE SEAFLOOR
HOLD IT STEADY IN ROUGH SEAS.
THIS REMOTE PLATFORM
IS THE ONLY STRUCTURE OF ITS KIND IN THE MEDITERRANEAN.
IT COLLECTS DATA AROUND THE CLOCK
TO HELP PREDICT WHEN A FLOOD IS ON ITS WAY.
FROM OCTOBER TO JANUARY, THIS IS THE ACQUA ALTA,
HIGH WATER, SEASON.
AND FLOODING TO VENICE IS ALMOST GUARANTEED.
RESIDENTS NEED TO KNOW
WHETHER THAT IT'S GONNA BE A DAY
FOR JUST WEARING RUBBER BOOTS,
OR IF THEY NEED TO PREPARE FOR THE WORST.
Narrator: THE TOWER WAS BUILT IN 1970,
FOUR YEARS AFTER THE WORST FLOOD TO EVER HIT VENICE,
THE GREAT FLOOD OF 1966,
WHEN THE LAGOON ROSE OVER SIX FEET ABOVE ITS NORMAL LEVEL.
ST. MARK'S SQUARE WAS UNDER SO MUCH WATER
THAT BOATS COULD SAIL OVER THE PIAZZA.
THE FLOOD WRECKED THOUSANDS OF HOMES
AND WILL NEVER BE FORGOTTEN BY THOSE WHO LIVED THROUGH IT.
[ SPEAKING ITALIAN ]
Narrator: "PEOPLE, ESPECIALLY THE ELDERLY, I REMEMBER,
"WERE STANDING AT THE WINDOWS OF THE FIRST FLOORS,
SCREAMING AND CRYING AND ASKING FOR HELP."
[ SPEAKING ITALIAN ]
Narrator: "THE FOLLOWING DAY WAS A DISASTER FOR ALL THE SHOPS.
"THEY'D ALL BEEN FLOODED.
"FRIDGES, CLOTHES, JEWELRY,
"EVERYTHING THERE WAS IN VENICE WENT UNDERWATER.
IT WAS TERRIBLE."
THE GREAT FLOOD LEFT 5,000 HOMELESS
AND CAUSED $6 BILLION OF DAMAGE.
VENICE'S FLOODS OCCUR WHEN PARTICULARLY HIGH TIDES
COMBINE WITH UNIQUE SYSTEMS OF AIR CURRENTS.
SITTING AT THE TOP OF THE ADRIATIC SEA,
VENICE IS VULNERABLE TO WINDS.
WARM WINDS FROM THE SOUTH
PUSH THE ADRIATIC SEA TOWARDS THE CITY.
BUT COLD WINDS FROM THE ALPS
CAN ALSO PUSH SEAWATER TOWARDS VENICE FROM THE NORTH.
THESE WIND SYSTEMS
CAN EVEN COMBINE TO CREATE THE PERFECT STORM,
THE SCONTRATA.
ATTACKING THE CITY FROM BOTH SIDES,
IT DRIVES THE SEA RIGHT INTO THE HEART OF VENICE.
THE ACQUA ALTA OCEANOGRAPHIC TOWER
IS THE CITY'S FIRST LINE OF DEFENSE AGAINST THESE FLOODS.
THE TOWER IS A HIVE OF TECHNOLOGY.
SENSORS MEASURE WIND SPEED AND DIRECTION,
HELPING SCIENTISTS DETECT STORMS
UP TO THREE DAYS BEFORE THEY STRIKE.
WATER GAUGES KEEP CONSTANT TRACK OF THE TIDE'S HEIGHT.
SEAWATER FLOWS PAST THE GAUGES
50 MINUTES BEFORE IT REACHES VENICE.
TRACKING ITS LEVEL HERE BUYS RESIDENTS VALUABLE TIME.
A SONAR DEVICE ON THE SEAFLOOR
TELLS SCIENTISTS THE HEIGHT OF INCOMING WAVES.
THE DATA IS SENT BACK TO THE MAINLAND IN REAL TIME,
HELPING THE CITY PREPARE
FOR THE WORST NATURE HAS TO THROW AT IT.
SHOULD THE WIND BECOME AS STRONG AS 20 KILOMETERS PER HOUR,
THEN WE HAVE A FAIR CHANCE FOR SEVERE FLOODS IN VENICE.
AND IF WE GET TO 50 KILOMETERS PER HOUR,
THEN WE REALLY WORRY.
Narrator: IF DATA FROM THE TOWER FORECASTS A FLOOD,
SIRENS ACROSS THE CITY GIVE ITS RESIDENTS TIME TO PREPARE.
HOTELS AND SHOPS BLOCK THEIR DOORWAYS WITH BARRIERS
AND RAISE ANYTHING PERISHABLE OUT OF REACH OF THE WATERS.
DURING SEVERE FLOODS,
MOST PEOPLE CAN MOVE UPSTAIRS
TO WAIT FOR THE HIGH WATERS TO PASS.
[ BELL RINGING ]
BUT NOT EVERYONE HAS THAT LUXURY.
[ SIREN WAILS ]
Narrator: VENICE, A CITY OF OVER 150 CANALS.
AND NO CARS OR TRUCKS ALLOWED,
WHICH CREATES A BIG CHALLENGE
FOR THE CITY'S EMERGENCY SERVICES, POLICE,
PARAMEDICS, AND FIRE CREWS.
IRONICALLY, FIGHTING FIRES IN THIS CITY OF WATER
CAN BE A DIFFICULT TASK.
ON JANUARY 29, 1996, A FIRE BROKE OUT AT LA FENICE,
VENICE'S 18th-CENTURY OPERA HOUSE.
FIRE CREWS GOT TO THE SCENE FAST.
BUT THERE WAS AN UNEXPECTED PROBLEM --
NO WATER.
THE NEAREST CANALS HAD BEEN DRAINED FOR REPAIR.
THIS FORCED US TO MAKE A VERY LONG CONNECTION
BETWEEN THE GRAND CANAL AND THE FENICE.
Narrator: TO REACH THE CANAL WATER NEEDED TO FIGHT THE FIRE,
THEY EXTENDED THEIR HOSES SO FAR THAT THE PRESSURE
DROPPED DANGEROUSLY LOW.
WE HAD MADE 100 METERS OF HOSES.
PART OF THE PRESSURE GETS LOST.
[ MAN SPEAKING ITALIAN ]
Bascià: THIS WAS A BIG PROBLEM FOR US.
BECAUSE WITHOUT WATER,
IT'S NOT POSSIBLE TO EXTINGUISH, YOU KNOW?
THE THEATER WAS COMPLETELY DESTROYED.
JUST EXTERNAL WALLS REMAINED.
Narrator: TO PREVENT FUTURE DISASTERS LIKE THIS,
ENGINEERS BUILT A BRILLIANT SOLUTION
INTO THE FABRIC OF THE CITY.
A NETWORK OF 700 HYDRANTS
FED BY 30 MILES OF PIPES
BURIED BENEATH VENICE'S SQUARES AND WALKWAYS.
THE PIPES PROVIDE A DEDICATED HIGH-PRESSURE WATER SUPPLY,
ENSURING CREWS CAN EXTINGUISH FIRES ACROSS THE CITY.
Bascià: WE ARE VERY HAPPY
WITH THE PRESENCE OF THE HYDRANTS HERE.
THEY GIVE US HIGH-PRESSURE AND FRESH WATER WHEN WE NEED IT.
AND THIS IS A GOOD THING FOR US.
Narrator: VENICE IS A RESOURCEFUL CITY.
BUT ONE PUZZLE REMAINS.
WITH VENICE'S LAGOON POSING SO MANY CHALLENGES,
WHY DID ANYONE BUILD HERE IN THE FIRST PLACE?
A CLUE LIES SEVEN MILES NORTH OF VENICE ON MAINLAND ITALY.
ANDREA NINFO FROM THE UNIVERSITY OF PADUA
BELIEVES AERIAL PHOTOGRAPHY CAN PROVIDE
SOME EXTRAORDINARY CLUES ABOUT THE EARLY VENETIANS.
[ SPEAKING ITALIAN ]
WE ARE TRYING TO SEE
WHAT LIES BENEATH THE SOIL WITHOUT DIGGING.
[ SPEAKING ITALIAN ]
Narrator: ANDREA LOOKS FOR SUBTLE PATTERNS IN THE FIELDS BELOW,
AREAS WHERE THE CROPS GROW POORLY.
Ninfo: UNDERGROUND ARCHAEOLOGICAL STRUCTURES
NORMALLY INHIBITS THE QUANTITY OF WATER AND NUTRITION
THAT THE PLANTS CAN RECEIVE.
Narrator: HE'S HUNTING FOR TRACES OF AN ANCIENT CITY
THAT REACHED ITS PRIME IN THE SECOND CENTURY B.C. --
ALTINUM.
ALTINUM WAS VERY IMPORTANT
BECAUSE IT COVERED AN AREA OF ABOUT TWO SQUARE KILOMETERS,
SOMETHING LIKE POMPEII.
Narrator: BACK ON THE GROUND, ANDREA ANALYZES THE CAMERA DATA.
HERE WE ARE IN THE NORTHERN PART OF THE CITY.
AND WE CAN CLEARLY SEE THE CITY WALLS,
THE MELODRAMATIC THEATER, AND A MONUMENTAL STRUCTURE.
Narrator: COMBINING HIS RESULTS WITH INFRARED IMAGES OF THE AREA
REVEALS ALTINUM'S VAST SCALE.
WE HAVE A REALLY REMARKABLE RECONSTRUCTION
OF THE CITY OF ALTINUM.
HERE, WE HAVE A CANAL.
THERE, WE CAN CLEARLY SEE THE WALL, THE THEATER,
THE MAIN SQUARE, THE FORUM.
AND THIS KIND OF LITTLE SQUARE ARE THE SHOPS.
Narrator: THE REMAINS OF ANCIENT ALTINUM
LIE BURIED AROUND THREE FEET BENEATH THE SURFACE.
ANDREA'S DETECTIVE WORK UNCOVERS STREETS OF DWELLINGS,
THEATERS, SHOPS,
AND CANALS CONNECTING THE CITY TO THE LAGOON.
ROMAN ALTINUM WAS A WORTHY FORERUNNER TO VENICE.
SO, WHAT HAPPENED TO THIS ANCIENT WONDER?
Ninfo: THE INHABITANTS WERE FORCED TO MOVE IN THE LAGOON
BY THE BARBARIAN INVASION
THAT STARTED IN THE FIFTH CENTURY A.D.
WITH ATTILA AND THE HUNS AND GOES ON FOR CENTURIES.
Narrator: AS WAVES OF INVADERS HIT THE REGION,
REFUGEES FROM ROMAN CITIES FLED TO THE ISLANDS OF THE LAGOON.
VENICE SOON BECAME A THRIVING TRADING PORT,
AND BY THE LATE 13th CENTURY,
IT WAS THE MOST PROSPEROUS CITY IN EUROPE.
TODAY, VENETIANS MAY BE SAFE FROM ANCIENT INVADERS.
BUT THEIR BATTLE WITH THE SEA CONTINUES.
FORTUNATELY, THERE'S A FORMIDABLE NEW WEAPON
THAT MAY FINALLY END THE WAR.
Narrator: VENICE, A CITY UNDER SIEGE AND CONTINUOUSLY SINKING.
SOME SCIENTISTS ESTIMATE
THAT THE OCEANS COULD RISE UP TO SIX AND A HALF FEET
BY THE END OF THE CENTURY.
IF THE LAGOON WATERS RISE THAT HIGH,
THE LOWEST PARTS OF VENICE COULD BE SUBMERGED
UNDER ABOUT THREE FEET OF WATER YEAR-ROUND.
OVER 80% OF THE CITY COULD BE PERMANENTLY FLOODED.
FLOODING IS ALREADY MORE FREQUENT...
AND A RADICAL SOLUTION IS NOW BEING DEPLOYED.
ONE THAT PROTECTS NOT JUST VENICE, BUT THE ENTIRE LAGOON.
ENRICO PELLEGRINI AND HIS TEAM
ARE BUILDING A CHAIN OF IMMENSE BARRIERS
AROUND THE LAGOON TO SEAL IT OFF FROM FLOODS.
A SERIES OF HOLLOW STEEL GATES MAKES UP THE BARRIER.
WHEN THE RISK OF FLOODS IS LOW,
THEY LIE FLAT ON TOP OF CONCRETE BLOCKS EMBEDDED IN THE SEAFLOOR.
WATER INSIDE WEIGHS THEM DOWN.
WHEN THE RISK OF FLOODING RISES,
PUMPS INJECT COMPRESSED AIR INTO THE GATES,
FORCING THE WATER OUT AND MAKING THEM MORE BUOYANT.
HINGES ALLOW THE GATES TO SWING UPWARD,
FORMING AN IMMENSE BARRIER AND STOPPING THE FLOODWATERS.
ONCE THE DANGER PASSES,
THE GATES REFILL WITH WATER AND DROP BACK ONTO THE SEABED.
78 GATES WILL FORM A MILE-LONG BARRIER
ACROSS THE THREE INLETS TO THE LAGOON,
SEALING IT OFF FROM ANY FLOODS.
THIS $7.5-BILLION PROJECT IS CODE NAMED MOSè,
AFTER THE BIBLICAL MOSES, WHO PARTED THE RED SEA.
THE ENGINEERS PREFABRICATE THE BARRIER ON DRY LAND.
EACH CONCRETE BLOCK FOR THE BARRIER BASE
IS 200 FEET LONG AND TAKES UP TO 12 MONTHS TO BUILD.
THE ENGINEERS SHIP THE COMPLETED BLOCKS AND GATES TO THE INLETS
AND CAREFULLY LOWER THEM TO THE LAGOON FLOOR.
FOR ENGINEER GIULIO DE POLLI, TODAY IS A CRITICAL DAY.
HE IS INSTALLING THE THIRD GATE.
THIS SUMMER IS VERY EXCITING.
BECAUSE, FINALLY, WE ARE INSTALLING THE GATES
AFTER SIX YEARS OF HARD WORK.
THIS IS THE THIRD GATE THAT WE SINK.
WE HAVE TO SINK THE GATES PRECISELY,
WITHIN MILLIMETERS OF TOLERANCE.
Narrator: THE GATE'S HINGES MUST LINE UP PRECISELY
WITH SLOTS ON THE BARRIER'S BASE.
STRONG CURRENTS OR WAVES COULD INTERFERE WITH THE SINKING.
EVERYTHING CAN GO WRONG.
EVERY GATE HAS ITS OWN PROBLEM.
Narrator: THEY SINK THE GATE AT AROUND 10 FEET AN HOUR.
AS THE CRANE LOWERS IT DOWN,
THE DIVE TEAM RELEASES TWO HUGE CAPS
COVERING THE SLOTS ON THE BARRIER BASE.
EACH CAP WEIGHS ONE TON.
SO, TO FLOAT THEM OUT OF THE WAY TO THE SURFACE,
THEY USE INFLATABLE AIRBAGS.
WITH THE CAPS REMOVED,
THE CRANE CREW LOWERS THE GATE INTO THE SLOTS,
TAKING THE BARRIER ANOTHER STEP TOWARDS COMPLETION.
THIS TIME, WE INCREASE THE SPEED OF SINKING BY HALF AN HOUR,
SO I'M HAPPY.
Narrator: 3 GATES DOWN, 75 TO GO.
THREE MONTHS LATER, THE BIG TEST.
WILL THE BARRIERS RISE?
[ MAN SPEAKING ITALIAN ]
[ APPLAUSE ]
WHEN COMPLETE IN 2016,
MOSè SHOULD HELP PROTECT VENICE FOR DECADES.
De Polli: THIS PROJECT IS A HUGE PROJECT THAT WILL MAKE A BETTER LIFE
TO VENETIAN PEOPLE AND MAKE ME PROUD.
Narrator: IT'S THANKS TO INGENIOUS INVENTIONS LIKE THIS
THAT PROP UP ICONIC BRIDGES AND BUILDINGS,
PROVIDE FRESH WATER FOR DRINKING
AND FIGHTING FIRES,
AND HELP CITIZENS PREPARE FOR FLOODS
THAT THIS SINKING CITY HAS SURVIVED SO LONG
IN THESE HOSTILE WATERS.