Original subtitles

DEEP BENEATH AMERICA'S MOST NOTORIOUS PRISON,

A RECENT DISCOVERY IS REVEALING OLD RUMORS

OF A SECRET TUNNEL SYSTEM.

DO YOU THINK THOSE ARE AIR POCKETS?

WAS ESCAPING ALCATRAZ MORE PLAUSIBLE THAN WE THOUGHT?

I'M GOING TO SEE WHERE IT GOES.

NEW GROUND-PENETRATING RADAR TESTS COULD REVEAL

A SIDE OF THE ROCK WE'VE NEVER SEEN.

THERE'S DEFINITELY SOMETHIN' RIGHT HERE.

MEANWHILE, AT THE BOTTOM OF LAKE MICHIGAN

LIES A MYSTERIOUS PATTERN OF ANCIENT ROCKS.

COULD THIS BE AN UNDERWATER STONEHENGE?

3-D PHOTOGRAMMETRY COULD UNCOVER NEW CLUES

HIDDEN ON THE ROCKS FOR MILLENNIA.

DO YOU SEE THAT?

HIDDEN JUST BELOW THE EARTH'S SURFACE,

THERE ARE COUNTLESS UNSOLVED MYSTERIES.

AND, TODAY, WE FINALLY HAVE THE TOOLS TO UNLOCK THEM.

LOOK AT THAT!WHOA.

I THINK THIS IS IT.

I'M ROB NELSON,

A SCIENTIST USING STATE-OF-THE-ART TECHNOLOGY

TO PEEL THE LID OFF OUR PLANET'S HIDDEN DEPTHS.

THE MOMENT OF TRUTH RIGHT HERE.

HOLY MOLY!

THESE ARE THE SECRETS OF THE UNDERGROUND.

Captions by VITAC-- www.vitac.com

CAPTIONS PAID FOR BY DISCOVERY COMMUNICATIONS

ALCATRAZ-- ONE OF THE WORLD'S MOST NOTORIOUS PRISONS.

BUILT ON A 22-ACRE ISLAND

SURROUNDED BY THE FRIGID SAN FRANCISCO BAY,

THIS ISOLATED FORTRESS ONCE HOUSED AL CAPONE,

MACHINE GUN KELLY,

AND DOZENS OF AMERICA'S WORST CRIMINALS.

ITS LOCATION AND DESIGN

MADE IT ALMOST IMPOSSIBLE FOR INMATES TO ESCAPE.

BUT THAT DIDN'T STOP SOME FROM TRYING.

OVER THE DECADES,

THERE WERE AT LEAST 14 SEPARATE ESCAPE ATTEMPTS

BY AT LEAST 36 DIFFERENT INMATES.

MANY HAD HEARD ABOUT A LEGENDARY NETWORK OF TUNNELS

THAT WERE SUPPOSEDLY CONCEALED BEHIND A CELLBLOCK WALL.

ONE OF THEM WAS JIM QUILLEN.

IN 1944, HE WAS WORKING A DETAIL IN THE KITCHEN

WHEN HE DISCOVERED A CRAWL SPACE THAT LED TO A BRICK WALL.

HE SPENT HOURS TRYING TO BREAK THROUGH

BEFORE HE WAS BUSTED.

THE EXISTENCE OF THESE TUNNELS HAS NEVER BEEN CONFIRMED.

BUT NEW HIGH-TECH RADAR SCANS SUGGEST THERE COULD BE

HIDDEN SUBTERRANEAN PASSAGEWAYS LEADING AWAY

FROM THE CELLBLOCK UNDERNEATH THE PRISON REC YARD.

SO, WAS JIM QUILLEN ONTO SOMETHING?

WHAT IS ON THE OTHER SIDE OF THAT WALL?

TO FIND OUT, I'M HEADING THERE MYSELF,

ARMED WITH STATE-OF-THE-ART SCANNING TECHNOLOGY TO EXPLORE

THE HIDDEN UNDERBELLY OF THE ROCK.

IN RECENT YEARS, GROUND-PENETRATING RADAR,

OR GPR FOR SHORT,

HAS UNCOVERED SOME INCREDIBLE LONG-BURIED SECRETS,

INCLUDING A MYSTERIOUS NETWORK

OF TUNNELS UNDER A NEARLY 2,000-YEAR-OLD MEXICAN PYRAMID

AND AN ANCIENT ROMAN GLADIATOR SCHOOL IN AUSTRIA.

TODAY, I'M BETTING GPR CAN HELP US

FIND ANY HIDDEN PASSAGEWAYS OR TUNNELS

THAT COULD HAVE OFFERED DESPERATE INMATES

A HOPE OF ESCAPE.

MY FIRST STOP IS THE MAIN CELLBLOCK,

WHERE ANY ESCAPE PLAN WOULD HAVE ORIGINATED.

MEETING ME THERE IS ALCATRAZ HISTORIAN JOHN MARTINI.

HEY, ROB. WELCOME TO ALCATRAZ.

YEAH. THIS PLACE IS INTENSE.

YEAH. AND COLD.

WANT TO GO INSIDE?

YEAH. OKAY.

SINCE THE MID-19th CENTURY,

ALCATRAZ HAS BEEN SYNONYMOUS WITH OUTLAWS.

DURING THE CIVIL WAR, CONFEDERATE SYMPATHIZERS

AND CITIZENS ACCUSED OF TREASON WERE HELD HERE.

AFTER THE SPANISH-AMERICAN WAR,

THE RISING INMATE POPULATION,

WHICH INCLUDED MANY SPANISH SOLDIERS,

WAS TASKED WITH BUILDING A LARGER CELL HOUSE--

THE ONE I'M IN RIGHT NOW.

THERE'S CELLBLOCKS ON BOTH SIDES.

A TOTAL OF 336 CELLS.

WOW.THERE WASN'T A LOT TO LIKE.

BUT THEY DID LIKE THE FACT THAT YOU HAD ONE-MAN CELLS,

SO YOU HAD PRIVACY.

YOU DIDN'T HAVE TO WORRY ABOUT BEING ASSAULTED BY YOUR BUNKIE.

THE DOWNSIDE WAS, YOU COULD SPEND

UP TO 23 HOURS A DAY IN THESE CELLS.

WHOA. WANT TO GO IN?

YEAH.

WOW. THESE ROOMS ARE SO TINY.

ONE BED, A PLACE TO WASH YOUR HANDS,

A PLACE TO USE THE TOILET.

IF I WAS IN A ROOM LIKE THIS,

AND I KNEW THAT I REALLY HAD NO CHANCE OF GETTING OUT,

I WOULD BE TRYING TO THINK OF A WAY OF ESCAPING.

ONE OF THE MOST NOTORIOUS BREAKOUT ATTEMPTS

WAS IN MAY 1946,

WHEN SIX PRISONERS STOLE WEAPONS AND KEYS

AND TOOK CONTROL OF THIS CELL HOUSE.

IT WAS DUBBED THE BATTLE OF ALCATRAZ.

THE BUILDING WAS UNDER SIEGE FOR THREE DAYS.

IF YOU LOOK AT THE WALLS, THOSE ARE ALL SCARS, SHRAPNEL,

BULLET RICOCHETS

THAT EMBEDDED THEMSELVES IN THE CELOTEX WALLBOARD.

THE UPRISING WAS SO WELL-EXECUTED

THAT THE WARDEN HAD TO BRING IN THE MARINES

TO TAKE BACK THE PRISON.

ULTIMATELY, ALL THE OFFENDING INMATES WERE CORRALLED.

THREE WERE KILLED IN THE PROCESS.

AND TWO MORE WERE LATER EXECUTED.

BUT THEIR FAILURE DIDN'T EXTINGUISH THE PERSISTENT HOPE

THAT AN ESCAPE FROM THE ROCK WAS POSSIBLE.

SHORTLY AFTER THIS CELLBLOCK WAS BUILT,

RUMORS BEGAN SWIRLING THAT THE INMATES

HAD ALSO CONSTRUCTED A SECRET NETWORK OF PASSAGEWAYS

UNDER THE NEW BUILDING THAT COULD CONNECT TO THE OUTSIDE,

LEADING MANY, LIKE JIM QUILLEN,

TO BELIEVE THEY COULD ACTUALLY USE THEM TO ESCAPE

IF THEY COULD BE FOUND.

IN HIS HEAD, QUILLEN HAD ONLY BEEN THAT FAR FROM FREEDOM.

AND THAT'S HOW DEEPLY SET

THE STORY OF THE SPANISH TUNNELS WAS.

JOHN TELLS ME ABOUT A LESSER-KNOWN SECTION

OF THE PRISON THAT SOUNDS LIKE A FITTING PLACE

TO START SCANNING THE WALLS FOR CLUES.

THERE'S ACTUALLY A LEVEL BELOW US

USED FOR SOLITARY CONFINEMENT.

SO RIGHT UNDERGROUND...YES.

...WHERE WE ARE RIGHT NOW...YES.

...THERE'S A ROOM, BASICALLY.

IT'S MORE THAN A ROOM. IT'S KIND OF A LABYRINTH.

IS THERE A WAY TO GET DOWN THERE AND ACCESS THAT

AND TAKE A LOOK AT IT FOR MYSELF?

I CAN TAKE YOU DOWN THERE.LET'S DO IT.

OKAY.

JOINING ME UNDER THE MAIN CELLBLOCK

IS GEOPHYSICIST STEFAN BURNS,

WHO IS AN EXPERT ON USING GROUND-PENETRATING RADAR

TO IDENTIFY HIDDEN POCKETS AND PASSAGEWAYS.

NEED HARD HATS.

FLASHLIGHT?

I'LL GO FIRST.OKAY.

THIS AREA WAS CALLED THE SPANISH DUNGEONS.

THIS DARK, DANK BASEMENT

IS WHERE INMATES WHO VIOLATED PRISON RULES WOUND UP.

TROUBLEMAKERS COULD BE KEPT HERE IN SOLITARY CONFINEMENT

FOR UP TO 19 DAYS IN THE DARK

WITH NOTHING BUT THEIR PRISON-ISSUE CLOTHING,

NOT EVEN A BLANKET.

SOME OF THE RUMORS THAT WERE SPREADING AT THE TIME

WERE THAT THE SPANISH DUNGEON LED TO SPANISH TUNNELS

AND THE ACCESS WOULD BE THROUGH HERE.

YES. ANYTHING THAT WAS BRICK

TO THESE GUYS SAID, "OOH, SPANISH TUNNELS."

SO EVERY GUY THAT DID TIME DOWN HERE,

WHEN HE GOT BACK UP TOP,

HE BLABBED AND GAVE RISE

TO THE STORIES OF SPANISH TUNNELS.

THE QUESTION IS,

COULD THERE HAVE BEEN MORE TO THESE RUMORS

THAN WISHFUL THINKING?

STEFAN AND I ARE GONNA TAKE SOME OF THIS HIGH-TECH EQUIPMENT

AND LOOK SPECIFICALLY

AT THE WALLS NEAR THE REC YARD

AND SEE IF WE CAN SEE ANYTHING.

THE PRISON RECREATION YARD

IS WHERE SUBTERRANEAN AIR GAPS WERE FIRST DETECTED

BY A TEAM OF SCIENTISTS IN 2013.

IF INMATES BURROWED UNDERNEATH IT,

THEIR TRAIL WOULD HAVE STARTED HERE.

THE REC YARD IS BACK THAT WAY.

SO WE'RE GONNA BE PARTICULARLY LOOKING

AT THE WALLS ON THIS SIDE.

READY TO GET THIS POWERED UP?

YEP.

STEFAN AND I ARE USING A TYPE OF GPR

THAT CAN PENETRATE MASONRY AND BUILDING STRUCTURES.

BE ABLE TO SEE THROUGH THE WALLS.

IT WILL TELL US IF THERE ARE ANY CHANGES

IN DEPTH BEHIND THE BRICK

THAT COULD SIGNIFY A TUNNEL OR PASSAGEWAY.

RIGHT UP HERE LOOKS FAIRLY CLEAR.

NOTHIN' REALLY ANOMALOUS.

I'M GONNA MOVE DOWN.

OH, LOOK. THERE YOU GO.

YOU CAN SEE SOMETHIN' RIGHT THERE.

IN ONE SECTION OF THE WALL, THE DATA SPIKES.

IT LOOKS LIKE WE COULD BE ONTO SOMETHING.

DO YOU THINK THOSE ARE AIR POCKETS?

WILL OUR RADAR POKE HOLES

IN THE ROCK'S INVINCIBLE REPUTATION?

LOOKS LIKE A CRAWL SPACE RIGHT IN THIS REGION RIGHT HERE.

AND LATER, I'LL TRAVEL TO THE SHORES OF LAKE MICHIGAN

TO INVESTIGATE A MYSTERIOUS PATTERN OF ROCKS

THAT SOME PEOPLE ARE CALLING AMERICA'S UNDERWATER STONEHENGE.

DO YOU SEE THAT?

THERE'S DEFINITELY SOMETHING THERE.

I'M IN THE INFAMOUS ALCATRAZ PRISON ON THE HUNT

FOR A LEGENDARY SYSTEM OF TUNNELS

THAT MAY HAVE OFFERED INMATES THE HOPE OF ESCAPE.

DO YOU THINK THOSE ARE AIR POCKETS DOWN THERE?

THAT COULD SIGNIFY AN AIR GAP ON THE OTHER SIDE OF THE WALL.

THIS IS THE OUTSIDE WALL

OF THE NOTORIOUS SPANISH DUNGEON,

A SUBTERRANEAN SECTION OF THE PRISON

EVERY BIT AS FOREBODING AS THE NAME IMPLIES.

FOR DECADES, RUMORS PERSISTED AMONG INMATES

THAT ITS WALLS CONCEALED TUNNELS THAT COULD BE USED TO ESCAPE.

AND I MAY HAVE JUST FOUND NEW EVIDENCE TO PROVE IT.

LOOKS LIKE A CRAWL SPACE RIGHT IN THIS REGION RIGHT HERE.

REALLY? YEAH.

IN AN OLD STRUCTURE LIKE THIS PRISON BASEMENT,

AN AIR GAP IN THE WALLS COULD BE ONE OF MANY THINGS.

BUT I'VE GOT ANOTHER TOY IN MY TOOL KIT

THAT MIGHT REVEAL A BIT MORE INTEL.

I HAVE A THERMAL IMAGING CAMERA.

ANYTHING I POINT AT, IT'S GONNA SHOW ME A HEAT SIGNATURE.

SO IF I POINT OVER HERE AT STEFAN,

YOU CAN SEE HIS NOSE IS COLDER THAN THE REST OF HIS FACE.

THAT MAKES SENSE. IT'S STICKING OUT.

THIS IS THE SAME SORT OF CAMERA THAT INSPECTORS WOULD USE

TO COME IN AND LOOK AT BUILDINGS.

I'M GONNA USE THE CAMERA TO TRY TO LOOK AROUND

AND SEE WHAT'S GOING ON BEHIND THE BRICK.

EVERYTHING'S PRETTY DARK.

THE THERMAL CAMERA WILL SHOW THESE SOURCES

IN VARYING SHADES OF COLOR.

WHITE, RED, AND YELLOW EQUAL WARM AIR.

BLUE, GREEN, AND BLACK MEAN COOLER AIR.

ON A FRIGID NIGHT LIKE TONIGHT,

ANY TUNNEL OR PASSAGEWAY BEHIND THESE WALLS

WILL REGISTER ON THE COLDER SIDE.

WHAT'S BACK HERE?

AS I WORK MY WAY ALONG THE DUNGEON'S OUTER WALL,

IT BECOMES CLEAR THERE IS SOMETHING UNUSUAL BEHIND IT.

IT IS A LITTLE BIT COOLER BACK HERE.

BUT THE THERMAL READINGS STILL AREN'T GIVING ME

ENOUGH DETAIL TO DETERMINE WHAT IT IS.

THEN, IN THE DEEPEST RECESS OF THE DUNGEON...

HOLD ON A SECOND.

I COME ACROSS SOMETHING CURIOUS...

HOLY MOLY.

...AN OPENING IN THE FLOOR.

OH, MY GOSH. LOOK AT THAT.

YOU CAN JUST FEEL THE COLD AIR PUMPIN' OUT OF THERE.

I'M GOING TO SEE WHERE IT GOES.

LOOKS LIKE A 7-, 8-FOOT DROP.

IMMEDIATELY, I BEGIN WONDERING

WHETHER THIS TUNNEL MIGHT CONNECT TO THE SPACES

WE FOUND BEHIND THE WALL.

BUT THERE DOESN'T SEEM TO BE ANY OBVIOUS LINK.

IF YOU LISTEN REALLY CAREFULLY...

YOU CAN HEAR THE OCEAN.

YOU CAN FEEL THE COLD AIR RUSHING IN HERE.

I HAVE MY GoPro RIGHT AT THE MOMENT.

I'M GONNA JUST GET A LITTLE BIT OF A PEEK WHAT'S GOIN' ON.

HOLY SMOKES.

YOU CAN SEE THAT THIS TUNNEL KEEPS GOING.

THIS IS EXACTLY

HOW I WOULD PICTURE MYSELF ESCAPING FROM ALCATRAZ.

BUT I WOULDN'T GET VERY FAR

BECAUSE IT TURNS OUT THIS IS A KNOWN SEWER TUNNEL

BLOCKED AT THE OTHER END BY AN IMPENETRABLE METAL GRATE.

ANY PRISONER TRYING TO BREAK OUT THROUGH HERE

WOULD HAVE FOUND HIMSELF TRAPPED BEHIND ANOTHER SET OF BARS.

SO, AS MUCH AS I LOVE CRAWLING DOWN PRISON SEWER PIPES,

I NEED TO STAY FOCUSED ON THE NEW LEAD

REVEALED BY OUR GPR--

THE AIR POCKETS BEHIND THE OUTSIDE WALL OF THE DUNGEON.

RIGHT NEXT DOOR TO IT IS THE PRISON RECREATION YARD,

WHERE ANOTHER STRANGE SET OF ANOMALIES

WERE RECENTLY DISCOVERED BY A TEAM OF SCIENTISTS

FROM TEXAS A&M UNIVERSITY.

THEIR GROUND-PENETRATING RADAR SCANS

REVEALED A SPRAWLING SET OF ANOMALIES

DIRECTLY ADJACENT TO THE MAIN CELLBLOCK.

COULD THOSE ACTUALLY BE TUNNELS THAT CONNECT TO THE GAPS

WE FOUND BEHIND THE DUNGEON WALL?

I NEED TO INVESTIGATE THE REC YARD MYSELF

TO GET A CLOSER LOOK.

REC YARD RIGHT OVER THERE.

THE NEXT MORNING, STEFAN AND I RETURN TO THE ROCK

WITH A DIFFERENT KIND OF GPR DEVICE.

SIMILAR TO THE WALL DEVICE WE USED YESTERDAY,

THIS GPR WORKS BY FIRING MICROWAVES INTO THE GROUND.

THESE ARE POWERFUL ENOUGH TO PENETRATE CONCRETE.

BUT ANYTHING BURIED WILL BOUNCE THE WAVES

BACK TO A RECEIVER ON THE MACHINE--

KIND OF THE WAY AN ULTRASOUND WORKS.

GPR DOES ALL THE WORK FOR YOU.

YOU JUST GOT TO BE ABLE TO INTERPRET IT.

ALL RIGHT. LET'S DO THIS.

GO AHEAD, WALK WITH IT AT A NICE, EVEN PACE.

EACH STEP YOU'RE TAKING,

IT'S SHOOTING OUT HUNDREDS OF DATA POINTS

AND THEN PLOTTING THEM ON THIS DISPLAY.

IF THESE SECRET SPANISH TUNNELS DO EXIST,

WE WILL SEE EVIDENCE APPEAR CLEARLY ON THE SCREEN.

THAT'S PROBABLY THE BOTTOM OF THE CONCRETE

THAT WE'RE GETTING RIGHT THERE, 'CAUSE IT'S FAIRLY HIGH UP.

THE GPR IS NOT REVEALING

MUCH OF ANYTHING IN MOST OF THE YARD.

BUT LOOK AT THIS.

BUT THEN...

YEAH.

AGAIN AND AGAIN, WE GO OVER THE AREA.

AND EACH TIME, THE READINGS SPIKE.

WOW.

THERE'S DEFINITELY SOMETHIN' RIGHT HERE.

COULD THIS BE THE SMOKING GUN

THAT PROVES THE LEGEND OF THE SPANISH TUNNELS?

IF IT IS, MAYBE THE ROCK

WASN'T QUITE AS IMPREGNABLE AS WE THOUGHT.

I'M IN THE REC YARD OF THE INFAMOUS ALCATRAZ PRISON

LOOKING FOR EVIDENCE

OF A LEGENDARY SYSTEM OF UNDERGROUND TUNNELS.

AND OUR GROUND-PENETRATING RADAR

HAS JUST UNCOVERED AN INTRIGUING ANOMALY.

THERE'S DEFINITELY SOMETHIN' RIGHT HERE.

AN AIR GAP OR A VOID UNDER THE SURFACE.

RIGHT NOW, IT LOOKS LIKE WE'RE LOOKING AT AN ARCH

THAT'S 18 FEET LONG,

AND THE BOTTOM OF IT IS ROUGHLY 51 INCHES,

SO ABOUT 4 FEET

AND GOIN' ALL THE WAY UP HERE TO THE TOP

ROUGHLY ABOUT-- WHAT IS THAT-- 6 INCHES. YEAH.

THE QUESTION IS, DOES THIS OPENING

CONNECT TO THE MAIN CELLBLOCK,

WHERE WE FOUND EVIDENCE OF AIR POCKETS

BEHIND THE ADJOINING WALL?

WE GOT A PERFECT LINE GOIN' RIGHT TO THAT CELLBLOCK.

ALL OF THESE ANOMALIES THAT WE'RE FINDING

APPEAR TO BE ABOUT 2 FEET UNDERGROUND.

THEY DON'T APPEAR TO BE SOMETHING

THAT IS REALLY NATURAL.

THEY APPEAR TO BE MAN-MADE.

IT LOOKS LIKE IT COULD BE A TUNNEL

HEADING RIGHT TOWARDS THE MAIN CELLBLOCK.

COMPILING THE DATA GATHERED ACROSS THE REC YARD,

WE'RE ABLE TO PEEL BACK THE LAYERS UNDERGROUND

AND GET A MORE COMPLETE PICTURE OF THESE ANOMALIES.

IT APPEARS AS IF THE HOLLOW POCKETS

RUNNING THROUGH THE REC YARD COULD CONNECT DIRECTLY

TO THE GAPS WE FOUND BEHIND THE PRISON WALL,

GIVING US A POTENTIAL PATH

DIRECTLY FROM THE SPANISH DUNGEON

OUT TOWARD THE OCEAN.

I CAME TO ALCATRAZ VERY SKEPTICAL

THAT THERE COULD BE SOME ELABORATE SYSTEM OF TUNNELS

STILL HIDDEN UNDER THE PRISON.

BUT GROUND-PENETRATING RADAR

IS NOW ALLOWING US TO SEE ALL SORTS OF THINGS

WE NEVER COULD BEFORE.

AND BETWEEN THE SCAN OF THE YARD

AND THE LARGE ANOMALY DETECTED BEHIND THE WALL,

I'M STARTING TO THINK THERE MAY BE SOME TRUTH

TO THOSE LONG-HELD RUMORS AFTER ALL.

BUT AS EXCITING AS THESE RESULTS ARE, THEY AREN'T CONCLUSIVE.

WE NOW KNOW THERE ARE AIR GAPS UNDER THE REC YARD

AND BEHIND THE CELLBLOCK WALL.

BUT THE GPR DATA DIDN'T GIVE US ENOUGH DETAIL

TO DECIPHER THEIR SHAPE AND SIZE.

SO I'VE GOT TO FIND SOME OTHER WAY

AT PEERING UNDERNEATH ALCATRAZ

TO DETERMINE WHETHER THE ANOMALIES

WE'RE SEEING IN THE DATA ARE ACTUALLY TUNNELS.

WHILE DIGGING FOR NEW RESEARCH ABOUT ALCATRAZ,

I CAME ACROSS ONE OF THE LEADING ARCHAEOLOGISTS

IN THE BAY AREA, PETER GAVETTE.

PETER HAS BEEN USING CUTTING-EDGE TECHNOLOGY

TO CREATE HIGH-TECH DIGITAL MAPS OF THE ROCK.

THESE BRAND-NEW MAPS CAN DISSECT THE COMPLEX LAYERS

OF HISTORY CONSTRUCTED ON AND UNDERNEATH THE ISLAND

IN WAYS WE NEVER COULD BEFORE.

THIS IS EXACTLY WHAT I'VE BEEN LOOKING FOR.

AND IT COULD BE THE FINAL PIECE I NEED TO COMPLETE THIS PUZZLE.

LET'S SEE.

SO, WHAT WE'VE BEEN DOING IS DIGITIZING THE MAPS.

AND THAT WAY, WE'RE ABLE TO OVERLAY ALL OF THEM

ON TOP OF EACH OTHER TO SEE WHAT HAPPENS

THROUGHOUT THE LAYERS OF HISTORY.

THE MAIN CELLBLOCK, THE RUMORED SITE OF THE SPANISH TUNNELS,

WAS BUILT BY SPANISH PRISONERS IN THE EARLY 20th CENTURY.

BUT PETER THINKS THE KEY TO UNDERSTANDING THE ANOMALIES

WE'VE FOUND IS TO LOOK BACK

AT THE EARLIER HISTORY OF THE ISLAND

BEFORE THE PRISON EVEN EXISTED.

BEFORE ALCATRAZ WAS A FEDERAL PENITENTIARY,

IT WAS A MILITARY FORTIFICATION PROTECTING THE BAY.

HE TELLS ME THAT THESE FORTIFICATIONS

WERE BUILT AROUND 1860

WITH THE CIVIL WAR LOOMING ON THE HORIZON.

SO, THIS IS ALCATRAZ AS IT IS TODAY.

PETER HAS BEEN USING OLD SURVEYING DATA TO CREATE

A WORKING MODEL THAT ISN'T JUST 3-D--

IT'S 4-D, MEANING WE CAN MOVE NOT JUST THROUGH SPACE,

BUT THROUGH TIME.

TO ACHIEVE THIS, HE FIRST HAS TO LINE UP

THE HISTORICAL MAPS WITH PRECISE GPS IMAGES OF THE ISLAND.

THEN, HE DIGITIZES THE CONTOUR LINES THAT SHOW ELEVATION.

THOSE EACH HAVE AN ASSIGNED VALUE.

AND WHEN WE ASSIGN THAT VALUE INTO THIS PROGRAM,

WE CAN THEN CREATE A 3-D IMAGE.

OH, AWESOME.SO THEN WE GET A VIEW OF--

OF THE ISLAND AS IT LOOKED IN 1867.

SO, WHAT WE CAN DO IS DRAPE OVER

THE CURRENT BUILDINGS AND TOPOGRAPHY.

OH, WOW.

FROM HERE, WE CAN LOOK AT ALCATRAZ

AND HOW IT'S CHANGED.

THIS DIGITAL MODEL IS STILL A WORK IN PROGRESS

AS NEW DATA CONTINUES TO BE GATHERED ACROSS THE ISLAND.

BUT I'M HOPING IT CAN SHED LIGHT

ON THOSE ANOMALIES WE FOUND IN THE DUNGEON

AND UNDER THE REC YARD.

COULD THEY REALLY BE REMNANTS OF A LEGENDARY ESCAPE ROUTE?

YEAH, ZOOM IN THERE A LITTLE BIT.

IN THIS AREA UNDERNEATH THE REC YARD,

WE WERE GETTING A LOT OF ANOMALIES GOING THIS WAY.

WHAT'S GOIN' ON?

LIKE, ARE THEY SOME SORT OF TUNNELS?

CYCLING THROUGH DATA SETS

FROM DIFFERENT DECADES, WE UNCOVER A LAYER

FROM THE MID-19th CENTURY WITH MARKINGS

THAT BEAR A STRIKING RESEMBLANCE TO THE AIR GAPS

I FOUND UNDER THE REC YARD.

WHAT IS THAT WE'RE LOOKING AT RIGHT HERE?

THESE ARE EARTHEN FORTIFICATIONS

THAT COVER BRICK STRUCTURES.

THAT STRUCTURE THERE PROVIDED MILITARY PERSONNEL COVER

FROM FIRE COMING FROM THE OCEAN.

SO WHAT WE'RE SEEING RIGHT HERE UNDERNEATH THE REC YARD

IS NOT TUNNELS, BUT CIVIL WAR FORTIFICATIONS.

RIGHT.

WOW.

AND JUST LIKE THAT,

THE TUNNELS ARE RELEGATED TO MYTH ONCE AGAIN.

THE DATA FROM THE 4-D MODEL

APPEARS TO SUGGEST THE ANOMALIES WE DETECTED UNDER THE REC YARD

WERE NOT ESCAPE TUNNELS.

INSTEAD, THEY WERE MOST LIKELY GAPS

BETWEEN CIVIL WAR ERA FORTIFICATIONS

FILLED OVER DURING CONSTRUCTION OF THE PRISON REC YARD.

THOUGH I WAS SKEPTICAL AT FIRST,

OUR FINDINGS GOT ME EXCITED

THAT MAYBE THE INMATES OF ALCATRAZ

REALLY DID KNOW SOMETHING WE DON'T,

THAT THEY HAD BUILT A SECRET NETWORK

OF ESCAPE TUNNELS THAT OFFERED HOPE

FOR AN OTHERWISE HELPLESS EXISTENCE.

BUT IT APPEARS THERE WAS NO WAY OUT UNDERGROUND AFTER ALL.

SO THAT MUST BE WHY THE ONLY PRISONERS

EVER TO ESCAPE FROM THE ROCK WENT UP INSTEAD OF DOWN.

IN 1962, THREE INMATES DUG THROUGH THEIR CELL WALLS

WITH SHARPENED SPOONS

AND REACHED A VENTILATION SHAFT UP TO THE ROOF,

WHERE THEY SLID DOWN A VENT PIPE 50 FEET TO THE GROUND.

THEY THEN MADE THEIR WAY TO THE BAY,

WHERE THEY SET SAIL ON A MAKESHIFT RAFT,

NEVER TO BE SEEN AGAIN.

THE FOLLOWING YEAR, THE ROCK CLOSED ITS DOORS FOREVER.

BUT DECADES LATER, THE LEGEND OF THE SPANISH TUNNELS PERSISTS.

IS IT POSSIBLE THEY ARE STILL HIDDEN

SOMEWHERE ELSE UNDER THE PRISON?

MAYBE FUTURE TECHNOLOGY WILL REVEAL SOMETHING WE'VE MISSED.

OR MAYBE, LIKE SOME OF THE INMATES

ONCE INCARCERATED HERE,

SOME SECRETS WILL NEVER LEAVE ALCATRAZ.

AND NOW I'M HEADING FROM ONE OF AMERICA'S MOST ICONIC SITES

TO ONE OF ITS MOST MYSTERIOUS--

LAKE MICHIGAN, ONE OF THE FIVE GREAT LAKES OF NORTH AMERICA

AND A PLACE PERMEATED WITH LEGENDS AND LORE.

ITS WATERS ARE A TIME CAPSULE OF LOST HUMAN HISTORY

DATING FROM THE PRESENT ALL THE WAY BACK

TO OUR EARLIEST PREHISTORIC ANCESTORS.

AND FOR ME, ONE OF THE MOST RECENT DISCOVERIES HERE

MAY BE THE MOST PERPLEXING.

WHILE SEARCHING FOR SHIPWRECKS,

A GROUP OF UNDERWATER ARCHAEOLOGISTS

STUMBLED ON SOMETHING THEY COULDN'T EXPLAIN.

SONAR SCANS OF THE LAKE BOTTOM

REVEALED A 1/4-MILE LINE OF ROCKS

CULMINATING IN AN ALMOST PERFECT HEXAGON--

AN ANCIENT, MYSTICAL SYMBOL.

THE ROCKS ALSO LIE IN CLOSE PROXIMITY TO TRIBAL LAND,

WHICH HAS LED MANY TO BELIEVE THIS IS NO ACCIDENT OF NATURE,

BUT A SACRED, MAN-MADE SITE LIKE STONEHENGE.

AND THAT'S NOT ALL.

SOME EVEN BELIEVE THEY CAN DECIPHER

A MAN-MADE CARVING ON THE FACE OF ONE OF THE ROCKS.

THIS RAISES SOME HUGE QUESTIONS.

FOR STARTERS, IF THIS IS MAN-MADE,

HOW DID IT GET 40 FEET UNDERWATER?

WHO PUT IT THERE, AND WHEN?

AND EVEN MORE PERPLEXING, WHAT EXACTLY IS IT?

TO PROBE THESE MYSTERIES,

I'M GOING TO EXPLORE THE SITE UP CLOSE AND PERSONAL

BY DEPLOYING STATE-OF-THE-ART TECHNOLOGY

THAT CAN CAPTURE THE CONTOURS

OF THE ROCKS IN UNPRECEDENTED DETAIL.

I THINK THAT'S SOMETHIN'.

FIRST, I NEED TO TALK TO THE MAN

WHO MADE THE INITIAL DISCOVERY--

UNDERWATER ARCHAEOLOGIST DR. MARK HOLLEY.

HE'S, ESSENTIALLY, THE GATEKEEPER.

IF YOU DON'T GO THROUGH MARK HOLLEY,

YOU DON'T SEE THE SITE.

HAVING GRANTED ME SPECIAL ACCESS,

MARK MEETS ME ON THE DOCK

WITH TRIBAL REPRESENTATIVE HANK BAILEY,

WHO HAS CLOSELY GUARDED THE SITE SINCE THE DISCOVERY.

WHAT DO WE NEED TO KNOW WHEN WE GO OUT THERE?

THIS SITE THAT WE'RE LOOKING AT

IS POSSIBLY A CEREMONIAL SITE.

WE DON'T WANT THE LOCATION OF THIS KNOWN YET.

MARK AND HANK SUSPECT THIS ROCK FORMATION

MAY NOT ONLY BE MAN-MADE, BUT SACRED.

SO THEY'VE KEPT ITS LOCATION TOP SECRET.

AND THEY'RE INTENT ON MAKING SURE IT STAYS THAT WAY.

WE WANT TO HAVE YOU BLINDFOLDED.

AND JUST TO BE CLEAR, GUYS,

IT'S GONNA BE THE CREW AND EVERYBODY.

EVERYBODY?EVERYBODY IN YOUR CREW.

SERIOUSLY? ALL RIGHT.

MARK EVEN MAKES US SURRENDER OUR CELLPHONES AT THE DOCK

SO WE CAN'T USE GPS TO PINPOINT OUR LOCATION.

THESE ARE SOME PRETTY SERIOUS MEASURES

TO PROTECT A FEW SUBMERGED STONES.

SO I CAN'T HELP BUT WONDER,

"WHAT DO THESE GUYS KNOW ABOUT THEM THAT I DON'T?"

BUT BEFORE I FIND OUT, IT'S TIME TO CUT THE CAMERAS.

I'M ON A QUEST TO INVESTIGATE A MYSTERIOUS PATTERN OF ROCKS

DISCOVERED UNDER LAKE MICHIGAN

THAT SOME ARE CALLING AMERICA'S UNDERWATER STONEHENGE.

I'VE SEEN THE ORIGINAL STONEHENGE UP CLOSE MYSELF.

IT'S A MYSTERIOUS SITE IN SOUTHWESTERN ENGLAND

THAT'S EVEN OLDER THAN THE EGYPTIAN PYRAMIDS,

DATING TO ABOUT 5,000 YEARS AGO.

IT'S A MEGALITHIC STRUCTURE MADE OF MASSIVE ROCKS

WEIGHING AS MUCH AS 50 TONS EACH.

THE ROCKS ARE STACKED ON TOP OF ONE ANOTHER

AND ARRANGED IN A GIANT CIRCLE.

SO IT'S CLEAR THAT STONEHENGE IS A MAN-MADE MONUMENT.

BUT THE ORIGIN OF THESE STONES

IN LAKE MICHIGAN IS LESS OBVIOUS.

WHILE THEY DO SEEM TO FORM A PERFECT GEOMETRIC SHAPE,

THEY AREN'T STACKED OR CONNECTED IN THE SAME WAY.

AND WHILE THERE IS EVIDENCE

THAT PREHISTORIC TRIBES ROAMED THE GREAT LAKES

FOR THOUSANDS OF YEARS,

VERY LITTLE IS KNOWN ABOUT THEM.

AND I HAVEN'T SEEN ANYTHING REMOTELY RESEMBLING

THIS FORMATION IN THE ARCHAEOLOGICAL RECORD.

SO, IF THIS IS MAN-MADE, WHO WOULD HAVE MADE IT, AND WHY?

ONCE WE'RE OUT IN OPEN WATER,

WE'RE ALLOWED TO TAKE OFF THE BLINDFOLDS

AND TURN THE CAMERAS BACK ON.

SO I JOIN UNDERWATER ARCHAEOLOGIST MARK HOLLEY

ON THE TOP DECK TO FIND OUT

WHY HE THINKS THIS DISCOVERY IS SO IMPORTANT.

TELL ME A LITTLE BIT HOW YOU FOUND IT.

WE WERE LOOKING FOR A SHIPWRECK.

ALL OF A SUDDEN, THIS LINE OF STONES COMES UP.

WE HAD NO IDEA OF WHAT IT WAS,

OTHER THAN IT DIDN'T LOOK TO BE NATURAL.

IT LOOKED TO BE ARTIFICIAL.

ONE LOOK AT THE OUTLINE OF THE ROCKS WAS ALL IT TOOK

TO CONVINCE TRIBAL ELDER HANK BAILEY

THAT THIS IS A CEREMONIAL SITE.

HANK'S ANCESTORS, THE ANISHINAABE PEOPLE,

WERE AMONG THE FIRST TO INHABIT THIS AREA.

HE BELIEVES HIS TRIBE'S PREHISTORIC FOREFATHERS,

HUNTER-GATHERERS WHO SETTLED THIS AREA

AFTER THE LAST ICE AGE,

PLACED THESE STONES HERE FOR A SACRED PURPOSE.

WHY IS IT SO IMPORTANT TO YOU?

ANISHINAABE CULTURE, WE REFER TO STONES

AS ANIMATE OBJECTS

BECAUSE THEY COME FROM THE MOTHER,

THE EARTH, WHO IS ALIVE.

WE REFER TO THEM AS MISHOMIS-- "GRANDFATHER."

THEY REINFORCE THAT WE HAVE BEEN HERE A LONG TIME.

AND THAT'S WHY WE'VE BEEN SO PARTICULAR

WITH YOUR CREW ABOUT...

YEAH. ...THE LOCATION.

BUT HOW COULD A SITE 40 FEET UNDERWATER BE SACRED GROUND?

IT'S UNLIKELY AN ANCIENT CIVILIZATION

WOULD HAVE DROPPED SIX STONES

INTO SUCH A PERFECT ARRANGEMENT FROM BOATS ON THE SURFACE.

BUT COULD IT BE POSSIBLE THAT IN THE TIME

OF HANK'S ANCIENT ANCESTORS,

THIS LAKE BED WAS HIGH AND DRY?

IF SO, THE POSSIBILITY

THAT THIS SITE IS MAN-MADE IS MORE LIKELY.

WHEN I STARTED RESEARCHING THIS STORY,

I KNEW THE SIZE OF THE GREAT LAKES HAD FLUCTUATED OVER TIME,

JUST NOT HOW MUCH THEY CHANGED OR WHEN.

SO I MET UP WITH LOCAL EXPERT BRIAN PRICE TO FIND OUT MORE.

BRIAN HAS BEEN STUDYING THIS PART OF THE COUNTRY FOR DECADES.

AND HE'S NOT THE LEAST BIT SKEPTICAL ABOUT THE PRESENCE

OF A MAN-MADE ROCK FORMATION BETWEEN LAKE MICHIGAN.

LAKE LEVELS HAVE CHANGED DRASTICALLY.

UH-HUH. BEEN MUCH HIGHER

AND THEN MUCH LOWER

AND THEN MUCH HIGHER AGAIN.

BRIAN EXPLAINS THAT WHEN THE GLACIERS

FROM THE LAST ICE AGE BEGAN TO MELT,

LAKE MICHIGAN STARTED TO SWELL.

BUT WHEN THE MELTING ICE EXPOSED A NEW CHANNEL

TO THE ST. LAWRENCE RIVER, THE MELTWATER DRAINED OFF,

AND THE LAKE SHRUNK DRAMATICALLY.

WE KNOW FOR SURE THAT, 10,500 YEARS AGO,

THE WATER LEVEL IN THE LAKE MICHIGAN BASIN

DROPPED PRECIPITOUSLY AND DRAINED

TO A MUCH LOWER LEVEL FOR AT LEAST 3,500 YEARS.

YOU'RE SAYING THAT THAT AREA

WAS NOT UNDERWATER 10,000 YEARS AGO?

RIGHT. 5,000 YEARS AGO,

THE WATER OVERRAN THAT SITE AGAIN

AS THE WATER LEVELS RAISED IN THE LAKE MICHIGAN BASIN.

RIGHT.

AND I'LL TELL YOU SOMETHING MORE.

WE KNOW THAT THE AREA WAS SETTLED.

IT WOULD HAVE BEEN A WONDERFUL PLACE FOR PEOPLE

TO LIVE NEAR THE COASTLINE CLOSE TO RESOURCES.

TRANSPORTATION'S EASY.

IT MEANS THAT PEOPLE COULD HAVE PUT THOSE STONES THERE.

ABSOLUTELY.

SO, BASED ON BRIAN'S RESEARCH, IT'S ENTIRELY POSSIBLE

THAT HUMANS COULD HAVE BUILT THIS SITE.

BUT THE QUESTION REMAINS, DID THEY?

AS A SCIENTIST, I KNOW THE ONLY WAY

TO DETERMINE THE TRUE NATURE OF THIS SITE

IS WITH EMPIRICAL EVIDENCE.

SO I NEED A CLOSEUP VIEW OF THE ROCKS

AND NOT JUST THE FLAT SONAR IMAGES

I'VE SEEN FROM ABOVE.

I NEED TO SEE THEM FROM BELOW.

WE GOT TWO PROPELLERS IN THE BACK.

WE GOT A PROPELLER ON TOP, PROPELLERS ON THE SIDES.

SO A MEMBER OF MARK'S TEAM

HELPS ME PREP THE CAMERA-MOUNTED R.O.V.,

OR REMOTELY OPERATED VEHICLE.

THIS ONE, NICKNAMED JAKE,

IS FULLY LOADED WITH THREE CAMERAS,

A GRASPING CLAW,

MEASURING LASERS, AND GPS NAVIGATION.

IT CAN WITHSTAND THE FRIGID WATER TEMPERATURE

OF LAKE MICHIGAN BETTER THAN ANY HUMAN.

AND IT CAN DIVE TO 1,000 FEET DEEP.

ALL RIGHT. LOOKS LIKE WE'RE IN A GOOD PLACE.

SO WE'RE GONNA GO DOWN.

SO, WE ARE ON THE BOTTOM.

THE R.O.V. GIVES ME A MUCH CLOSER LOOK AT THE SITE

THAN THE RADAR SCANS.

AS A MARINE BIOLOGIST, I'VE SPENT A LOT OF TIME

EXPLORING UNDER WATER THIS WAY.

AND AT FIRST GLANCE, NO OBVIOUS TRACES

OF HUMAN PRESENCE JUMP OUT AT ME.

BUT ONE STONE IN PARTICULAR

HAS DRAWN SPECIAL ATTENTION FROM MARK'S TEAM...

I THINK THAT MIGHT BE OUR STONE HERE.

...BECAUSE THEY THINK IT HAS A CARVING ETCHED ONTO ITS FACE.

YEAH, YOU CAN SEE IT LOOKS PRETTY ROUNDED OFF.

SO I THINK THIS FACE RIGHT HERE--

THIS LINE HERE, THIS LINE HERE,

I THINK, MAKES UP THE POTENTIAL CARVING.

FINDING A CARVING WOULD CONFIRM THAT THIS SITE IS MAN-MADE

AND OPEN UP A WHOLE NEW SET OF QUESTIONS.

BUT THE RESOLUTION FROM THE R.O.V.'s CAMERA

ISN'T SHARP ENOUGH TO TELL FOR SURE.

YEAH. I MEAN, HONESTLY,

IT IS REALLY HARD TO SEE.

I MEAN, IT'S SOMEWHAT LOW RES. IT'S HARD TO TELL RIGHT NOW.

I THINK WHAT WE'RE GONNA HAVE TO DO IS GET IN THE WATER.

WE DON'T EXCAVATE ANYTHING. WE'RE NOT TOUCHING ANYTHING.

WE'RE JUST GOING DOWN, LOOKING, TAKING PICTURES.

OKAY.

MARK AND HANK HAVE AGREED

TO ALLOW JUST ONE DIVE TO THE SITE.

NOW I'M AMPED.

IF I'M GOING TO SOLVE THE MYSTERY

OF THIS UNDERWATER STONEHENGE, THIS IS MY ONE SHOT.

I'M DESCENDING TO THE BOTTOM OF LAKE MICHIGAN

TO GET A CLOSER LOOK AT A MYSTERIOUS SITE

SOME HAVE CALLED AMERICA'S UNDERWATER STONEHENGE.

AT FIRST, I EXPECTED THIS PECULIAR-SHAPED FORMATION

WOULD TURN OUT TO BE JUST A NATURAL ANOMALY.

BUT I'M STARTING TO BELIEVE IT MAY BE SOMETHING MORE.

FOR ONE THING, THE GEOLOGICAL RECORD INDICATES THIS SITE,

NOW 40 FEET UNDERWATER,

MAY HAVE BEEN ON DRY LAND FOR MILLENNIA

AFTER HUMANS ARRIVED HERE.

AND ARCHAEOLOGICAL EVIDENCE SUGGESTS THIS AREA WAS INHABITED

BY PREHISTORIC AMERICANS LONG BEFORE THAT.

BUT MOST STRIKING ARE THE IMAGES FROM OUR R.O.V. CAMERA

THAT SHOW WHAT COULD BE A MAN-MADE CARVING

ON ONE OF THE ROCKS.

COULD THIS BE SOME OF AMERICA'S OLDEST ARTWORK

OR JUST ANOTHER RANDOM ACT OF NATURE?

THERE'S ONLY ONE WAY TO FIND OUT.

I CAN MAKE OUT A SERIES OF INDENTATIONS

THAT COULD BE A CARVING.

BUT THE VISIBILITY IS TOO POOR FOR ME TO TELL FOR SURE.

SO I'M GOING TO TRY OUT A NEW PIECE OF TECHNOLOGY

THAT SEES THE ROCK BETTER THAN I CAN--

AN ADVANCED TECHNIQUE CALLED STEREO PHOTOGRAMMETRY.

AND IT ALLOWS SCIENTISTS TO CREATE 3-D MODELS

FROM TWO-DIMENSIONAL PHOTOGRAPHS.

PLACING SCALE BARS AROUND THE ROCK AS A POINT OF REFERENCE

AND PHOTOGRAPHING IT FROM MULTIPLE ANGLES,

I'LL BE ABLE TO STITCH TOGETHER A DIGITAL MODEL OF THE ROCK

FOR MORE DETAILED DIGITAL INSPECTION.

A LINE OF SIGHT IS CONSTRUCTED FROM THE CAMERA

TO VARIOUS COMMON POINTS ON THE ROCK.

THEN, THE TRIANGULATION OF THESE LINES

FROM MULTIPLE PHOTOS CAN DETERMINE

THE 3-D LOCATION OF THOSE POINTS

AND BUILD AN ACCURATE 3-D RENDERING OF THE ROCK,

WHICH I CAN ANALYZE IN DETAIL ONCE I'M BACK ON DRY LAND.

AFTER I'VE GATHERED ALL OF THE EVIDENCE I CAN,

WE MAKE OUR WAY BACK TO SHORE.

I'M CONVINCED THERE'S SOMETHING PECULIAR

AT THE BOTTOM OF LAKE MICHIGAN.

HOPEFULLY, THE 3-D MODEL WILL GIVE ME THE TOOLS

I NEED TO DETERMINE THE TRUTH

ABOUT THESE ROCKS ONCE AND FOR ALL.

IF THIS SITE REALLY WAS MADE BY MAN,

IT MUST HAVE SERVED A SPECIFIC PURPOSE.

SO, WHAT COULD IT BE?

I KNOW THAT SEVERAL EARLY CULTURES

USED STONES TO TRACK THE POSITION OF THE SUN

AND THE STARS IN THE SKY.

IN FACT, THERE'S A WELL-KNOWN STONE FORMATION IN WYOMING

CALLED THE MEDICINE WHEEL,

WHERE THE ROCKS ALIGN WITH CERTAIN STARS

ON SPECIFIC DATES OF THE YEAR.

IT WAS AN EFFECTIVE TOOL TO PREDICT

WHEN THE SUMMER SOLSTICE WOULD OCCUR,

ALLOWING NATIVE PEOPLE TO BETTER TIME

WHEN TO HARVEST THEIR CROPS.

COULD THAT BE WHAT'S HAPPENING WITH THESE ROCKS

RIGHT HERE IN LAKE MICHIGAN?

WHEN IMAGES OF OUR UNDERWATER ROCKS

ARE COMPARED WITH THE MEDICINE WHEEL,

I NOTICE A GLARING OMISSION.

NOT ONLY DOES THE MEDICINE WHEEL HAVE 28 AXES,

PROVIDING MORE ACCURATE LINES OF MEASUREMENT,

BUT OUR SITE DOESN'T HAVE

A PRECISELY MARKED CENTRAL FOCAL POINT,

A KEY FEATURE IF YOU'RE TRYING TO CHART

THE SUN'S POSITION IN THE SKY.

SO IT SEEMS UNLIKELY THIS HEXAGON OF SIX ROCKS

WAS USED TO TRACK THE SUN OR STARS.

THE STORY BEHIND THESE STONES STILL ELUDES ME.

BUT THERE'S ONE MORE MAJOR CLUE

THAT COULD CRACK THE CASE-- THE CARVING.

TRYING TO ORIENT MYSELF HERE.

THERE'S DEFINITELY SOMETHING THERE.

I NEED TO GET A CLOSER LOOK. LET ME GET MY TABLET OUT HERE.

ALL RIGHT, IF I JUST KIND OF OUTLINE THESE INDENTATIONS,

BASICALLY TAKING EVERYWHERE WHERE I SEE AN INDENTATION...

STRIPE THERE. STRIPE DOWN THIS WAY.

THERE'S, LIKE, SOMETHIN' THERE.

LOOKS TO ME LIKE MAYBE THESE ARE SOME SORT OF LEGS IN HERE.

THIS COULD BE AN EAR.

IF YOU LOOK AT THIS, AND YOU START SKETCHING IT,

ONCE YOU OUTLINE THE LINES, IT LOOKS LIKE WE--

IT LOOKS LIKE A FREAKIN' MASTODON.

UNBELIEVABLE.

A MASTODON CARVING ON A ROCK

THAT HASN'T SEEN DAYLIGHT IN AT LEAST 5,000 YEARS.

THIS IS HUGE.

MASTODONS ARE AN ANCIENT ANCESTOR

OF ELEPHANTS AND WOOLLY MAMMOTHS.

THEY WERE ONE OF THE LARGEST LAND ANIMALS

EVER TO ROAM NORTH AMERICA,

STANDING UP TO 10 FEET TALL AND WEIGHING UPWARDS OF 6 TONS.

MASTODON FOSSILS HAVE BEEN UNCOVERED

ALL ACROSS THE EASTERN U.S., INCLUDING IN PLACES

THAT COULD HAVE BEEN LINKED TO LAKE MICHIGAN

ALONG THE SAME MIGRATION ROUTE.

IN NEIGHBORING OHIO, AT THE BURNING TREE GOLF COURSE

OUTSIDE OF COLUMBUS,

EXCAVATORS DIGGING IN A PEAT BOG

UNCOVERED THE MOST COMPLETE SKELETON

OF AN AMERICAN MASTODON EVER FOUND.

BUT MORE RECENTLY, A DISCOVERY IN A FLORIDA LAKE

LED SCIENTISTS TO A STARTLING REVELATION.

BUTCHERED MASTODON BONES WERE FOUND ACCOMPANIED

BY MAN-MADE TOOLS,

PROVING THAT MASTODONS AND HUMANS COEXISTED

IN NORTH AMERICA THOUSANDS OF YEARS EARLIER

THAN PREVIOUSLY THOUGHT--

BETWEEN ROUGHLY 15,000 AND 10,000 YEARS AGO

BEFORE MASTODONS WENT EXTINCT,

WHICH GIVES US AN APPROXIMATE DATE

AS TO WHEN OUR SITE MAY HAVE BEEN MADE.

AND IT COULD BE AT LEAST TWICE AS OLD AS STONEHENGE.

SO, IF THIS IS A MASTODON CARVING,

IT STRONGLY SUGGESTS THIS SITE IS MAN-MADE

AND DATES IT TO AT LEAST 10,000 YEARS AGO.

BUT ONE QUESTION STILL REMAINS--

WHAT PURPOSE DID IT SERVE?

I'M SETTING OUT TO SOLVE THE FINAL PIECE

OF OUR PREHISTORIC MYSTERY

WITH A LITTLE HELP FROM AN ARCHAEOLOGIST

WHOSE OWN RECENT DISCOVERY COULD BE THE LAST MISSING PIECE.

LET ME SHOW YOU WHAT WE'VE SEEN IN LAKE HURON.

YOU PROBABLY SAW SOMETHING

THAT LOOKED PRETTY SIMILAR TO THAT, RIGHT?

YEAH. JUST LIKE THAT.

MY INVESTIGATION INTO A MYSTERIOUS PATTERN

OF ROCKS LYING 40 FEET BELOW LAKE MICHIGAN

HAS YIELDED SOME INTRIGUING REVELATIONS.

FOR STARTERS, THIS SITE WAS ON DRY LAND FOR MILLENNIA

DURING A SPAN OF TIME WHEN PREHISTORIC TRIBES

OF HUNTER-GATHERERS ROAMED THE CONTINENT.

SO A COMMUNITY OF ANCIENT PEOPLE

COULD, INDEED, HAVE PLACED THESE ROCKS.

AND THE PRESENCE OF WHAT APPEARS TO BE A CARVING OF A MASTODON

ON ONE OF THEM IS STRONG EVIDENCE THAT THEY DID.

BUT ONE KEY QUESTION STILL REMAINS--

WHY WERE THESE ROCKS PLACED IN A PERFECT HEXAGONAL SHAPE?

WHAT PURPOSE DID THEY SERVE?

TO FIND OUT, I'M MEETING UP

WITH ARCHAEOLOGIST DR. JOHN O'SHEA.

RECENTLY, HE MADE A DISCOVERY IN NEARBY LAKE HURON

WHICH COULD SHED LIGHT ON OUR MYSTERY.

LET ME SHOW YOU AN EXAMPLE OF WHAT WE'VE SEEN IN LAKE HURON.

IF YOU LOOK AT THIS,

YOU'LL SEE THAT YOU'VE GOT THIS LONG LINE

OF KIND OF EVENLY SPACED ROCKS

OUT WHERE THERE'S NOTHING ELSE THERE.

YOU PROBABLY SAW SOMETHING

THAT LOOKED PRETTY SIMILAR TO THAT TODAY, RIGHT?

YEAH. JUST LIKE THAT.

UNDER LAKE MICHIGAN, THERE'S A LONG LINE OF ROCKS

LEADING DIRECTLY TO OUR HEXAGON.

AND HUNDREDS OF MILES AWAY

UNDER A COMPLETELY DIFFERENT LAKE,

THERE APPEARS TO BE A VERY SIMILAR CONFIGURATION.

SO THERE COULD DEFINITELY BE A CONNECTION HERE.

WHAT DO YOU THINK IT IS?

I CAN MAKE A PLAUSIBLE ARGUMENT

THAT IT'S A HUNTING STRUCTURE THAT THE ANCIENT HUNTERS USED

KNOWN AS A DRIVE LANE.

DR. O'SHEA EXPLAINS THAT DRIVE LANES

HAVE BEEN USED BY HUNTERS FOR THOUSANDS OF YEARS

AS A WAY TO HERD LARGE GROUPS OF ANIMALS

ALONG A SET PATH TOWARD A KILL ZONE,

WHERE HUNTERS LIE IN WAIT.

I'D LIKE TO SHOW YOU ONE THAT IS STILL USED TO THIS DAY.

THIS IS THE EDGINGTON DRIVE LANE IN NORTHERN CANADA.

YOU SEE THIS LINE OF STONES BEHIND THE HUNTER.

THAT'S ACTUALLY A CARIBOU DRIVE LANE.

AND IN THE FOREGROUND, YOU'LL SEE A CIRCLE.

AND THAT CIRCLE IS A HUNTING BLIND

THAT LOOKS A LOT LIKE THE ONE YOU WERE ON.

THE CARIBOU WON'T JUST STEP OVER THAT?

THEY WILL NOT.

THAT'S ENOUGH TO CHANNEL THE MOVEMENT OF THE ANIMALS.

MANY PREY SPECIES THAT LIVE IN HERDS

INSTINCTIVELY AVOID CROSSING BARRIERS,

EVEN IF THEY'RE JUST PAINTED LINES.

I GREW UP IN NEBRASKA, AND AT CATTLE CROSSINGS,

THEY PAINT STRIPES.

AND THE CATTLE WON'T STEP IN THE STRIPE

BECAUSE THEY'RE AFRAID OF THEIR HOOF GOING THROUGH IT

LIKE IT'S-- LIKE IT'S AN OPENING.

THE ANCIENT HUNTERS KNEW THAT THEY COULD SUGGEST

WHERE THE ANIMALS OUGHT TO MOVE-- INTO ZONES,

WHERE THEY COULD THEN AMBUSH THEM.

THE DISCOVERY OF THESE ANCIENT DRIVE LANES

GIVES US SOME KEY INSIGHT INTO THE ANCIENT HUNTERS

WHO USED THEM.

THEIR SIZE AND SCALE SUGGEST THEY WERE CREATED

BY A LARGE GROUP OF ORGANIZED PEOPLE

CAPABLE OF WORKING TOGETHER AS A TEAM.

MAYBE FUTURE EXCAVATIONS

WILL REVEAL MORE ABOUT THE HUNTERS AND THE HUNTED

WHO ROAMED THE GREAT LAKES IN PREHISTORIC TIMES.

BUT OUR SCIENTIFIC ANALYSIS OF THIS LONG-LOST ROCK FORMATION

HAS ALREADY TAUGHT ME MORE THAN I EVER THOUGHT IT COULD,

LIKE THE FACT THAT THE GREAT LAKES

WERE ONCE MUCH SMALLER THAN THEY ARE NOW,

THAT MASTODONS AND PEOPLE CROSSED PATHS ON A LANDSCAPE

NOW LOST BENEATH THE WAVES,

AND THAT OUR PREHISTORIC ANCESTORS

HAD ADVANCED STRATEGIES

FOR ROUNDING UP VAST HERDS OF PREY.

THIS CURIOUS COLLECTION OF STONES

HAS PRESERVED ITS SECRETS FOR MILLENNIA.

IT JUST NEEDED SCIENCE TO DECODE THEM.