Underground Marvels (2019–…): Season 2, Episode 3 - Cincinnati's Secret Caverns - full transcript

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[narrator] Below this historic
Cincinnati neighborhood

lies a forgotten underworld.

We found tunnels that have been
sealed up for over a hundred years.

[narrator] What does this
vast subterranean maze,

reveal about this city's past?

Thousand of miles away,

overlooking the Baltic Sea.

Is a secret, underground Danish fortress,

carved into a cliffside.

What pivotal role did this
concealed stronghold play

during the Cold War?



This really is on the frontline.

[narrator] And located 170
feet below this major waterway

in Liverpool,

lies a breath-taking feat
of underwater engineering.

- [turbine whirring] - Nobody had
seen anything of this scale before.

[narrator] Throughout history,

life underground has
captured our imagination.

It's a very frightening but
also very beautiful experience.

[narrator] Now, we're
taking you further and deeper.

There's all kinds of wild theories
about what could be below.

[narrator] To unearth the mysteries,

the secrets, and the wonders of these...

Underground Marvels.

[narrator] Lurking beneath the
heart of Downtown Cincinnati



are remnants of Ohio's best kept secrets.

Located 30 feet below the city streets,

is a network of abandoned
tunnels and caverns

with a rich history that
shines light on its origins.

The magic of Cincinnati
is right down these steps.

[narrator] Who built this
underground labyrinth?

And why was it abandoned?

All of this industry
and all of this culture

starts to collapse all at once.

[narrator] How are they now being revived?

Being able to get a
piece of living history,

it just fills me with joy.

[narrator] For decades, Cincinnati
has had a lot going on above ground.

But what makes this historic city unique

is what's hidden below it.

In the 1830s and 40s, 100s of 1000s of
German refugees fled to the United States,

in hope of a life free from
repression and inequality.

In Cincinnati,

they settled in the historic
Over-The-Rhine district.

And they brought with them
their most treasured product,

beer.

The United States is often
referred to as a nation of immigrants.

[narrator] Julie Carpenter
is an architectural historian

specializing in the region's rich history.

By the time, Over-The-Rhine
was fully developed,

the neighborhood was
between 60 and 75% German.

You see a lot of buildings
that have German.

Language on them.

What we know as Republic Street today,

was originally called Bremen.

[narrator] Cincinnati already had
an established brewing industry.

But the newest residents added
something distinctly German.

[Julie] For as long as there
have been people in Cincinnati

people have been brewing beer.

The earliest breweries were run by English,

Irish, Scottish

And they were making,
traditional English-style beers,

ales and porters.

[narrators] While the English
breweries remained above ground,

the German ones relied
on subterranean chambers

to craft their delicious concoctions.

We're walking into the fermentation level

of the Jackson brewery.

[narrator] Mike Morgan is
Cincinnati's resident beer expert.

[Mike] This room looks
huge and cavernous now.

But it would have been packed,

with fermenting beer in the 1800s.

Huge wooden vats

going up and down both sides of it.

The only real difference
between a lager and an ale

is that lager yeast

requires cool temperatures to ferment,

and ale yeast ferments
at room temperatures.

[narrator] At their peak,
nearly 35 breweries

were producing more than 30
million gallons of beers per year.

As demand grew,

local business owners
had to dig additional tunnels

and cellars to accommodate production.

[Mike] All these lager
cellars have two levels.

And on the upper level,
they would ferment the beer.

And on the lower level, they would age it.

[narrator] Most of the beer
would be consumed locally.

But soon, the German lager's popularity

spread far beyond the city limits.

[Mike] It was sending a
lot of what was made here

down to New Orleans.

So if you went to the French Quarter,

good chance was

it came from right here
in these lagering cellars.

[narrator] Demand increased exponentially.

Over-The-Rhine and the city of Cincinnati

experienced an economic
boom due to beer production.

So much so, the city earned its nickname

as the Beer capital of the world.

But building cellars large enough to house

not just fermentation tanks
but also thousands of barrels

of the finished product was
no easy task in the 1850s.

The enterprising brewers got creative.

[Steve] The magic of beer in Cincinnati

is right down these steps.

[narrator] Steve Hampton
works for an organization,

revitalizing the brewing district.

[Steve] So we're 30 feet underground
in the Crown brewery cellars.

They use arch stone construction.

They use stone floors.

And they're typically built
by very specialized contractor

cellar diggers.

It was very hard to do.

Uh, 30-40 feet underground.

You were in the middle of a
dense, urban neighborhood

where there were people
working and living and playing

literally right next to you.

[narrator] What brewers soon realized

was that their underground
recipe for success

had a lethal side effect.

Fermentation produces

significant amounts of carbon dioxide.

Built up CO2 would not only make
these tunnels off-limits for people,

it would also starve the
fermenting process of oxygen.

And slow or even stop
the production of beer.

[Steve] They built these
series of ventilation shafts.

They look like fireplace,

but they're actually ventilation shafts.

They could actually use
the natural stack effect

and let the warm air out of this space,

and keep fresh air in here.

[narrator] Ventilation solved
the carbon-dioxide problem,

but keeping the cellars cold enough,

for the lager fermentation process,

needed further innovation.

[Steve] Early on, they would use ice,

that they would harvest from the lakes,

and the rivers and the canals,
literally cut that in blocks,

pack it away with the
barrels of beer down here.

[Mike] There's a lot of cons to ice.

It's expensive, it's unpredictable.

It also melts and that
creates all sorts of problems.

So they started using
artificial refrigeration,

as soon as that was possible.

And when they did, there would have
been lines crisscrossing through here.

And it was ammonia that
was run through those lines.

[narrator] While the early brewers
had addressed the temperature issue,

they unknowingly introduced
another complication.

[Mike] Ammonia remains
a very effective coolant.

We don't use it today
because it will kill you.

[Steve] They would often times have
ammonia leaks from the cooling systems,

that would kill draft horses.

It could even overcome
the uh, workers down here.

[narrator] Coolant leaks were
just one of the many dangers

facing workers in Cincinnati's
underground breweries.

[Steve] They were often at risk of being

injured by blowing kegs
or kegs falling down,

like, massive kegs of
couple hundred pounds each,

breaking legs and ankles.

Beer was part of your pay.

And so, often you were drinking
while you were on the job,

and so, drinking and
old cellars weren't always,

the most conducive to safety so
we had a lot of accidents that way.

[narrator] As the breweries
continued to boom,

they managed to adapt and prosper.

However, by the turn of the century,

a nationwide shift was
about to cast a dark shadow,

over Cincinnati's beer making industry.

[Mike] All of this industry
and all of this culture,

it really all starts to collapse.

All at once.

[dramatic music playing]

[narrator] In the 19th Century,
innovations in beer-making

required breweries to
undergo major upgrades,

Cincinnati was at the
forefront of these changes.

Pasteurization in 1864. That's a big deal.

You don't have to consume it immediately

without it spoiling.

[Mike] We then get into
technology around steel.

So we go from wooden vat to big metal tanks

that are easier to clean
and get the bacteria out of.

And we also start to
see revolutions in glass.

And then in 1892, you know,
we have the crown bottle cap.

[dramatic music playing]

[narrator] Despite these investments,

society was changing.

And the industry was
in for a rude awakening,

[Mike] The United States
enters World War One in 1917.

When that happens,
all of that "German-ness"

that made Over-The-Rhine,

such a unique European feeling place,

that all becomes bad.

So that's really the first blow.

Prohibition goes into
effect nationally in 1920.

And so, all of this industry
and all of this culture,

it really all starts to collapse

all at once.

[narrator] By 1918,

laws were passed forcing
breweries to shut down.

And for many years,
things looked very bleak

for the Over-The-Rhine district.

Some breweries tried to
survive by brewing illegally.

But police raids squashed most efforts.

And soon the Cincinnati
breweries were seemingly forgotten.

Now, decades later,

there's been a recent
drive to revive the area.

Combined with a new popularity
for high-quality craft beer,

the Over-The-Rhine district
is being brought back to life.

Breweries are reopening,

and the community is once again embracing

it's vibrant past.

As these tunnels and cellars are renovated,

some unexpected discoveries have been made.

We found a new access to tunnels

that have been sealed up for over 100 years

here in Cincinnati.

[narrator] Bret Kollmann
Baker is a chemical engineer

turned craft-brewer,

now operating in Over the Rhine.

He's found an unusual
use for the unearthed cellars.

[Brett] These tunnels were
discovered three, four years ago

when the new tenants bought the building.

The punched this whole out

and what did they discover

besides a massive pile of rubble

and a big freaking hole in the ground.

Put your lights on, it's
a little dark down here.

So, this is F. & J.A. Linck

brewery lager tunnels.

Look at this.

What we have here is the top of a barrel.

You let it ferment, then you
let it lager, which is aging.

[narrator] Brett realized that the
original wood fermenting tanks

could still be harboring
life in their timbers.

Yeast lives up to an inch-deep in wood.

There's a really good chance

that this yeast has sporulated,

which means that it is in a hard shell

and it can basically just hibernate

for as long as it wants in that,

until it get dropped into

liquid conducive to its growth,

so we're talking sugar,
we're talking nutrients.

[narrator] Brett took swabs
from the Linck brewery,

and sent them to a lab to be tested.

One swab.

Now, it doesn't look like we got anything

to the naked eye, but that doesn't matter,

'cause we just need a tiny little spore

that you're not even gonna see.

We're gonna dip it into our jar,

seal it back up,

and hopefully, get
something good out of it.

[narrator] Out of 100 swabs taken,

one successfully picked
up spores of brewer's yeast.

Tiny micro-organisms that survived

in the barrels for a over a century.

Being able to get a piece of living history

that survived from before prohibition

here in Cincinnati is just, a...

I mean, it's just... It
just fills me with joy.

[narrator] The yeast spores were
grown under controlled lab conditions

and returned to Brett to create

a brand new 100-year-old beer.

Today, craft breweries are
on the rise across the country.

But in Cincinnati, it's more than a trend.

It's a tradition

that dates back more than 150 years.

On the south coast of Denmark,

overlooking the Baltic Sea,

is a cliff face hiding both
military and pre-historic mysteries.

We're ready if you decide to attack us.

[narrator] Carved directly into the rock

is an impenetrable fortress

with more than a mile of
underground passageways

tough enough to withstand a nuclear bomb.

[speaking]

[narrator] As the cold war escalated,

this base was equipped
with the latest technology,

and built to be on the frontline.

[speaking]

[narrator] In the late 1940s,

Denmark was reeling from the
impact of the second world war.

It had only recently been
liberated from Nazi control

and the country
desperately wanted to rebuild.

But just as one war was
ending, another was beginning,

As political and military tensions grew

between the east and the west,

NATO called upon Denmark

to play a major role in the cold war

as the first line of defense

from Russia's red banner fleet.

Denmark was sometimes
called the guardian of the Baltic.

Usually, people just
say the cork in the Baltic,

'cause Baltic is kind of like the
bottle in these really narrow straits

you have to get out of
to get out of the Baltic.

[narrator] Iben Bjornsson
is a historian and curator

at the Stevnsfort museum.

She works to preserve the memory

of the crucial role this
cork in the Baltic played.

In 1949, Denmark joined NATO,

and with that, it was
solidified in a future war

if the enemy would be the Soviet Union.

The Soviet Baltic fleet was the main fleet.

In a war, they would
have to move that fleet

through the Danish straits,

and out into the open sea.

So the purpose of Stevnsfort
was to close off the sound.

Denmark's task was to hold the cork in

and prevent the entire Baltic fleet

from coming out into the Atlantic.

That was a pretty important task.

[narrator] War could potentially
break out at any moment,

and there was nothing protecting
Denmark from the enemy.

The Stevnsfort would be the first to know

about an imminent attack.

And it would be their
job to alert the world.

Sometimes for British,
but especially Americans,

for them, the actual battlefield in a war

was something far away.

You have the enemy right there.

It really is on the front
line of the Cold War,

but also would be on the
frontline of an actual war.

[narrator] Stevnsfort was
intentionally constructed

so the Danish could not
only see an attack starting,

but potentially had a chance to intervene.

You would have sea mines sort of covering

this stretch of water,

and then you would have the big guns.

Now these two guns were
to support the minefields.

And shoot down the minesweepers

which would be sent in advance.

Denmark alone would not stand a chance

against the Soviet fleet.

The task for Denmark with the NATO was to

hold the line for long enough

for reinforcement to come from the west.

[narrator] Building a
sub-terranean fortress

that could survive the first strikes

of enemy aggression was crucial.

But unlike some military
complexes built during this time,

Stevnsfort had one huge advantage.

Fire.

[narrator] Strategically located
on Denmark's south coast,

Stevnsfort was in prime position

to monitor the Baltic
Sea during the Cold War.

Any maritime vessel friend or foe

would not go unnoticed.

No expense was spared in building the fort.

[Iben] With all the tunnels
and nooks and crannies,

it's 1.7 kilometers.

It's built into nearly identical sections,

to support the two big guns on the surface,

each section supporting one gun.

[narrator] An attack
was considered so likely,

that when building the fort,

the tunnel layout was
designed with a breech in mind.

[Iben] Where we're standing
now, you can see the hallway.

It makes sort of a little
bend or a little break

and that's because if the
enemy takes one section,

he's not able to stand down there,

and shoot into the other section.

[narrator] What was unique to Stevnsfort,

in comparison to many other
military bases around the world,

is that it's existence wasn't classified.

NATO wanted the communists
to know it was there.

The Russians were also supposed to know

that we had a military
installation waiting for them here,

pointing out towards the Baltic

and we're ready if you decide to attack us.

When determining where to
locate their cork in the Baltic,

Denmark deliberately chose
this site for several reasons.

Possibly the most important

is that it could withstand a nuclear blast.

Fire!

[narrator] Answers to how and why

can be found 65 million years ago.

[speaking]

[narrator] Dr. Jesper Milan

has spent his career studying
the geology at Stevnsfort.

The rock formations along this coast

are unique in their specific make-up.

And it was no mistake

that this location was selected

for the construction of Stevnsfort.

[speaking]

The impact absorption of the rock

is the result of several
fortuitous stages in its evolution.

[speaking]

[speaking]

If the fortress was under nuclear attack,

the alternating layers
would behave like a mattress,

gradually bending,

absorbing and dissipating the shock wave.

Should war strike Stevnsfort,

the base had to remain operational.

This required it to be equipped with

the very latest in surveillance technology.

[Iben] This is the heart
of the underground.

If war broke out,

you would have your
operation sensor down here.

This was really the top of the line

electronic surveillance gear in the '80s.

Red ships are water packed ships.

Of course, the blue ships
are our own NATO ships.

The green ships are civilian

and the white ships are unidentified.

This is where you would have your overview

of all traffic going through the sound.

[narrator] Throughout the Cold War,

there were times when
tensions nearly boiled over

to full-on conflict.

[Iben] During some of the major crisis,

this place went into high
alert, which means lockdown.

Cuban Missile Crisis was one.

You had people down here
for a week, week and half.

Hungary, 1956 was another

and Czechoslovakia, 1968 was another.

You would have the order "Clearfort."

Which means everyone is underground.

You don't get radio signals down here.

You didn't get newspapers.

So they would just basically

receive no news.

I imagine that would
have been, uh, quite scary.

[narrator] Despite the
depth of the fortress,

there were risks inside and out.

None more so than the Russian Navy,

who remained unnervingly close.

[speaking]

[narrator] Visible to all the world,

Stevnsfort was constantly
under threat during the Cold War.

Troops stationed here knew
that should war break out,

they would likely be the
very first Russian target.

[speaking]

Brian Hecto Sorenson,

is a retired naval officer,

who served at Stevnsfort.

[speaking]

[narrator] The Polish Crisis began in 1981

with a worker uprising.

And threatened the communist
stronghold in the country.

As the Soviet Union
planned a military intervention,

naval activity greatly increased

right on Denmark's doorstep.

[speaking]

Stevnsfort went into lockdown
in anticipation of an attack.

[speaking]

[narrator] During the lockdown,

food and water had to be readily available.

And the secure power supply maintained.

[Iben] If war were to break out,

you knew that relatively fast,

the main powerlines would be cut.

The fort is built to be
self-sufficient for three months.

That's why you had your emergency generator

and that one is on diesel oil.

[narrator] The troops below
ground were on constant alert.

[speaking]

[narrator] One of the most important jobs

was operating the formidable cannons,

aimed at the narrow
passage of the Oresund Strait.

[speaking]

[narrator] The guns had a colossal range.

But they needed to be fired accurately,

if they were to be effective.

It was a multistep process.

[speaking]

Inside the gun, you could
have a crew of 18 people in here.

Here we have the main gunner

and then you would have
people manning sort of each side.

This is actually the main barrel.

Down here, you can climb all
the way down to the underground.

[narrator] With the threat of
the Cold War and nuclear warfare

looming over Stevnsfort,

it was fitting that during construction,

scientists discovered this site
was no stranger to devastation.

[speaking]

[narrator] Thankfully, the Cold
War never escalated to the point

that Stevnsfort's powerful
defenses had to be put into action.

By the early '90s, the
Soviet Union collapsed.

And without an enemy to defend against,

the fort was eventually closed in 2000.

It's role now is to serve as
a memory of the Cold War,

on a frontline that few knew about.

The cliffs surrounding the fortress

are evidence of one extinction event.

The fortress itself,

evidence of an extinction event avoided.

In the northwest of England,

lies the city of Liverpool.

Beneath the Mersey river

is one of the greatest man-made
engineering achievements

of the 20th century.

At over two miles long,

it was unprecedented for its time.

Nobody had seen
anything of this scale before.

[narrator] Prior to being known
as the home of The Beatles,

the global port of Liverpool
was experiencing growing pains.

Travelling from one side of the
Mersey to the other required ferries

and lots of time.

With the increasing
popularity of the automobile,

people needed a quicker way to do business.

And engineers had the answer.

It was all done by
handpicked small explosives.

[narrator] So how did the tunnel designers

figure out how to beat
the river at its own game?

[speaking]

[narrator] For centuries, ships
transporting goods across the world,

have navigated the River
Mersey into the port of Liverpool.

The river was also a vital means
of moving goods and people locally.

In the early 1900s, everything
had to come across by ferry.

People, livestock, horses and carts.

[narrator] Yet the use of motor vehicles

was increasing exponentially
around the globe.

And engineers were searching for
solutions to handle a new phenomenon

called traffic jams.

In 1922 alone, 640,000 cars

trying to get from Liverpool

across the Mersey to Birkenhead,

caused chaos.

The traffic was building
up, either side of the river.

So, something had to be done.

[narrator] Local engineers got to work,

attempting to solve a problem

that no one in the world
had successfully done yet.

Sir Archibald Salvidge,

one of the city engineers at the time,

appointed a committee to
tackle the infrastructure problem.

The committee proposed two options.

Build a bridge or a tunnel.

The bridge was a really expensive
option compared to a tunnel.

They also knew, having
come out of the First World War,

that a bridge across the river

would be a target for enemy bombers.

[narrator] After several years of debate,

the committee voted for a tunnel.

The next challenge

was to find an engineering
genius who could build it.

Determined to keep
the traffic flowing freely

in the city of Liverpool,

Sir Archibald Salvidge asked the
government for financial support.

Support to build the tunnel.

The Chancellor of the
Exchequer was Winston Churchill.

And they agreed to fund it
to the tune of £2.5 million.

Sir Archibald Salvidge
appointed Sir Basil Mott,

who was one of the real titans
of British engineering at the time

to lead on the project.

Mott had overseen some of the
country's largest engineering feats,

including bridges over the Thames

and installing the first escalators
to London's Underground.

But nothing would surpass the
enormous engineering challenges

he was about to face.

[speaking]

[narrator] In the early 20th century,

the world was trying to
cope with a new phenomenon,

traffic jams.

In Liverpool, engineers were
attempting to combat this problem

by building an underwater tunnel

on a scale that had never
been attempted before.

Dr. Hyung-Joon Seo of
the University of Liverpool

has worked on some of the
UK's biggest tunneling projects.

[speaking]

The plan was to build
a two-mile long tunnel

170 feet below the River Mersey.

But with no modern
equipment at their disposal,

the excavation alone was
a dangerous undertaking.

[Smith] This tunnel was all dug by hand.

Seventeen hundred men
working on it at its peak,

and it was all done by
hand picks, small explosives.

Engineers decided to start
with two exploratory pilot tunnels

on each side of the river,

to make sure conditions
were safe to continue digging.

The goal was for the two tunnels
to eventually meet in the middle.

[Smith] To accurately meet in the middle,

they had a depth-measuring stick.

They would shine a light across
to the next depth-measuring stick

and make sure they were coming
out at the same level each time.

After three years of back-breaking work,

on April 3rd, 1928,

the two teams met under the river.

[Smith] When they met in the
middle, they were less than an inch out.

So it was very accurate work back then.

Even though the pilot
tunnels were a success,

the main tunnels were much larger,

meaning engineers had
to dig in every direction.

And soon only four feet of
rock stood between the workers

and the raging river above.

One wrong move could
have been catastrophic.

Modern underground
construction uses boring machines

to seal the tunnels as they go.

But the workers tunneling
in the early 20th century

had rudimentary technology

to keep the mighty River Mersey at bay.

Since over 1.2 million tons of
rock needed to be excavated,

experimentation was necessary

to find the best solution
to waterproof the walls.

[speaking]

The workers installed
100,000 cast-iron linings,

weighing more than 70,000 tons,

all by hand to support the tunnel.

[speaking]

Yet, water wasn't the only issue
engineers had to contend with.

[whirring]

In the early 20th century,

groundbreaking designs
for the Mersey Tunnel

had managed to protect the
tunnel and its crew from the river.

The next challenge was to rid
the tunnel of lethal exhaust fumes.

With combustion engines passing under
the Mersey at a rate of 4,150 per hour,

the risk of a catastrophic
disaster was high.

The project's lead
designer, Sir Basil Mott,

needed to devise an ingenious plan

or this airflow issue would
threaten the entire project.

Using a mixture of longitudinal
and transverse ventilation,

they designed a unique system
to vent toxic fumes from the tunnel.

The air is now coming
down from the fresh air fan,

and it comes down the
shaft and it meets these walls.

These walls we call our banana walls,

because they're curved.

The longitudinal system funneled air

along channels running
parallel to the road.

It was then diverted
away and the air filtered.

[Smith] The air comes round
the corner, along this air invert.

To get it on the road deck, you've got
this series of holes on the underside.

So the air travels up through those,

hits a U-shaped
structure which sends it off

across the road deck
at about exhaust level.

The transverse ventilation used a
system of ducts in the walls and ceilings

to inject air and remove exhaust gases.

[speaking]

To sustain this system over
a two-mile underwater tunnel

required serious power,

capable of delivering 2.5 million
cubic feet of fresh air every minute

and withdrawing the same amount.

This huge fan is 28 feet wide.

It weighs 25 tons.

It can actually create a wind
speed of about 36 miles an hour.

The building had to be built around
them because of the sheer size of them.

Having overcome this mammoth undertaking,

on July 18th, 1934,

the tunnel was officially
opened by King George V.

This tunnel was actually described
as the eighth wonder of the world

when it opened, because nothing
had been built on this scale before.

People came on holiday to Liverpool

just to drive through the tunnel,

because they'd never experienced
driving underwater before.

Not only was it deemed
the longest and largest tunnel

ever attempted beneath
a major body of water,

it was by far the most modern
and technologically advanced.

Two underwater junctions
would service four lanes of traffic

under the Mersey,

between two entry and exit
points on either side of the river.

The Mersey Tunnel is a 24-hour operation.

It never sleeps.

Today, Liverpool has a dedicated team

to maintain this massive
underwater transit system.

Paul Heaton is one of the
engineers taking on this crucial role.

The workmanship back in the 1920s and 1930s

of the original builders
of the tunnel was fantastic.

It's left us with a really
good structure to maintain.

Yet the power of the river
surrounding the tunnel is relentless

and every day water leaks through.

Underneath us now is a huge sump.

It spans the width of the Queensway Tunnel.

This pump manages to pump
out 145 meters cubed of water

every minute.

Pushed out by the pump into
the main sewers in Birkenhead.

If these pumps fail,
disaster will likely follow.

The water would fill up the sumps,

and it would actually fill up these rooms.

We wouldn't have a tunnel
because it would be underwater.

But a lot has changed
since the tunnel first opened.

During its first year, nearly 2
million vehicles passed through.

Today, 12.8 million vehicles travel safely
through the Mersey Tunnel every year.

This infrastructure is key to the
economic success of the area.

The ambition and engineering prowess

of the early-20th century builders
who dared to tame the Mersey

is nothing short of inspiring,

and remains truly impressive

even by 21st-century standards.