Original subtitles

We would use the modern-day technologies

And in fact, if we look, we can see on the rotunda the outline

Of where the original pediment should have met the rotunda.

These columns come from egypt, shipped down the nile,

And then shipped across the mediterranean,

And then shipped up here.

I think we can imagine that there were many,

Many places where they might have broken,

Or where the ships might have sunk

Or something might have happened.

Narrator: If this build's ever going to happen,

We've gotta make some concessions, too.

Andrews: You know, for a large, domed structure,

Because these columns here are ten feet too short.

Of reinforcing steel,

And that would provide an enhanced level of safety.

Narrator: Here's the good news.

If we use reinforcing steel,

We can make our concrete dome much larger.

The original one was 43 meters or so across.

Let's say we build one that's --

I'd say let's make it twice as big.

Let's make it 86 meters across.

Narrator: We're going to do everything we can to keep

Our modern-day temple upright.

It's been standing strong for 2,000 years.

That came right out of the rail world.

Narrator: They built a dome that moves.

We can built an even bigger,

Unreinforced concrete dome, right?

Andrews: For sure, we could make it larger.

But the more important add to that is, we wouldn't do it.

And we wouldn't do it because of engineering standards

And technologies and building codes and things like that.

Our building codes are designed

So that there's a life safety component to them.

Narrator: We don't want our pantheon to become famous for crumbling.

This ancient dome has passed the ultimate safety test.

Narrator: We're imagining what it would take

Construction has progressed a lot since then,

But maybe not enough to match our modern-day ambitions.

Can it be done? Absolutely, but at what cost?

Narrator: We're probably not going to be able to build

A bigger, unreinforced dome,

But the romans had to make compromises, too.

Higgins: The pantheon is a remarkable building,

But not everything went according to plan.

This façade would have been even more remarkable

Had it been built with the size of columns

That were designed for it.

Thinks it'll take to build today.

Narrator: But before we start worrying about repairs,

We've got to finalize our construction plans.

So, how many people do we need,

And how long is it going to take?

Well, here's the ancient benchmark.

In order to build the pantheon,

It would have taken 1,100 laborers

About ten years to build it.

If we were to build it today,

I think there are some efficiencies

We can take to try to speed up the process.

Narrator: Here's what the team in toronto

This building will last for a long time.

On site, we'd need probably somewhere in the range of,

Depending on the phase of the construction,

From 50 people to maybe 250 people.

Our design team might be starting off with 5,

Going to 20, going to 100 people itself.

Narrator: We'll put it at 350 people at peak production.

So, how long?

From start to finish, the whole thing we could

Probably do in a little more than three years itself.

Narrator: So, let's say it's 3 1/2 years

With a max capacity workforce of 350 people.

Is back to replace the glistening pvc shield

To build a modern-day pantheon in new york city.

We wanna build it out of concrete,

And we'll need to put a plan into place

To ensure that our structure

Stays standing for generations to come.

I think you build up a maintenance plan

With a proper budget and proper solutions

To keep that structure looking good.

And that's all in the planning.

Narrator: That was the plan for the rogers center.

Three decades later, the same construction company

It's based on a rail itself

That protects this steel dome.

Massé: So, the crew's actually up there

Removing some of the existing membrane

And putting a new membrane back on top.

In order for them to do that,

They need to do it from a swing stage,

Which rides over top of the existing membrane.

They go up. They cut it out.

And then they put the new membrane back down.

The building itself is actually still in great shape,

So as long as they keep the maintenance up,

And thanks to the building material we've chosen,

Mccallum: He has a massive palace outside the city of rome at tivoli,

And historians believe he had some input into its design.

And many of the elements of the pantheon are echoed

In some of the buildings and rooms at tivoli.

Some people used to think that perhaps hadrian himself

Designed the pantheon,

But it's unlikely that he would have really had the experience

To build such a sophisticated building.

It's extremely likely that he had a lot of input into it,

And that it represents his ultimate dreams

Of what a building should be.

Narrator: We're dreaming of an architectural wonder of our own,

That had been his great passion throughout his life.

We can give it any look we want.

Concrete can dry into so many different forms,

It has fed the creative appetites

Of many modern architects.

There was a movement in the '60s, '50s

And '60s called brutalism.

Brutalism comes from the french word brute

Which means raw, pure.

Concrete is ideal for this kind of nakedness.

This rawness.

Narrator: Brutalism fell out of style by the 21st century,

All the dry ingredients, chemicals, waters, everything.

Just about any color and any variety you want.

Narrator: With the right aggregate,

We think we can build a pantheon on par with the original.

But a little new-age chemistry

Might just tip the scales our way.

So, what's the last ingredient in concrete?

Add mixtures.

Chemical concoctions that vary widely,

Based on the application and location of your build.

We'll make sure we choose the right chemical

Add mixture to protect against new york's harsh winters.

Nickerson: So, this is where we're able to mix everything,

But structures like this one at the university of miami

This is where we basically mix it all together,

Measure it all out, dump it into the back of the truck,

Let the truck work its magic.

Narrator: So, we've got all of the ingredients

We'll need to build our modern-day pantheon.

But what's it going to look like?

This pantheon's design was overseen

By ancient rome's biggest architecture aficionado

Who just so happened to be the emperor himself.

When hadrian became emperor in 117,

This allowed him, really, to indulge something

Three of which move along this custom track.

The pantheon's got a concrete roof

Sitting on concrete frames down below.

Narrator: The official name is the rogers center,

But it was originally named the skydome.

Construction began in 1987,

And this ballpark sprung up in just 2 1/2 years.

Blackman: So, the skydome was basically

The first of its kind in the world.

We had to build a fully retractable dome stadium

That could open a roof in 20 minutes.

It had never been done anywhere in the world.

Narrator: The dome is actually four separate roof panels,

We've got a roof sitting on concrete frames here.

So we're up in the rail system of panel one.

The rail system of panel one, panel one actually has

Four rails -- a lower rail, an upper rail,

An outer rail, and an inner rail.

These are really quite heavy rails,

And they're located on a very precise geometry,

A circular radius geometry, and this is the bogey

That picks up the first arch truss itself.

You know, this thing is really a derivative

Of pure train technology, the bogey system itself.

It's based on a rail type of wheel.

And modern brutalism.

Scream brutalism is back.

The thomas b. Murphy design studio was named 2018's

Building of the year by world architects,

An international network of architects, engineers,

And designers.

El-khoury: The popularity of the building

Testifies to the power of concrete

And to the simple minimalist design of the building.

Narrator: This is the design inspiration we've been looking for.

Narrator: We're imagining an all-concrete pantheon,

A 21st century mash-up of classical antiquity

Now, all we need is the green light.

So, let's take the form of the pantheon

And re-create it entirely from concrete.

Now, how are we going to build it?

Can we beat the ancient romans' record

And build an even bigger, unreinforced concrete dome?

Maybe we can ask whoever built this 55,000-seat

Domed baseball park in toronto, canada.

Andrews: They had to figure out how to build

A concrete dome roof unreinforced,

And then they had to figure out how to sit that roof

On a series of concrete frames just like we do here.

Narrator: We could use a similar pump to reach the heights

Depending on where the forces were

And the load conditions on that roof.

It's quite interesting.

Ochsendorf: Some of the concrete in the pantheon

Is almost light enough to float in water.

Narrator: Today, it's no problem for us

To pump up our concrete one story at a time.

So, up here at the actual structural slab now,

Boys are getting everything placed down,

So we're doing a structural floor here today.

So they've got all the form work in place.

We're using the pump to get it up here to this elevated level.

They actually used different kinds of aggregates,

Of our new pantheon dome, but we've got another idea.

We're going to pour and set our dome off-site.

And when the concrete dries,

We'll fly it in with a fleet of aerial cranes.

Securing it on top of our concrete frame.

Now, for the interior work.

It's very important how you finish every suite

From the minute detail.

I think some people don't see that, but I see it.

Narrator: We're going to spare no expense

To turn this concrete frame into the world's most

The wooden form work has to remain in place.

Narrator: Once our structural frame has hardened,

We've got to construct the crowning achievement

Of our new pantheon.

But wait.

How did the romans pull this off?

What was really technically challenging

Is building a dome with that span.

It's a very, very wide span to build.

You have to put a wooden framework across the dome,

And then lay the concrete on top.

While the concrete on top was setting,

And until it becomes hard and can carry loads,

State-of-the-art convention center.

There was a kind of element of hope at that moment

That the dome wouldn't collapse.

Ochsendorf: There was a conscious effort by the builders

To reduce the weight,

And therefore, reduce the loads on the walls

And on the foundations.

Andrews: The romans were really smart in that

They had different kinds of aggregate.

They had dense, heavy aggregates,

And they had lighter aggregates.

And in the roof of the pantheon,

But most of all, through architecture.

Our best chance to outlive this pantheon

Is a lifetime of maintenance.

Higgins: We're very lucky to have the pantheon.

It survived when so many other roman buildings have not.

It's been repaired.

It's been structurally supported.

Otherwise, you know, buildings don't survive.

If they're not used, they don't survive.

Narrator: People need to love it, use it, and take care of it.

That's how you become an architectural icon.

The pantheon has had enormous influence across almost

Every creative human endeavor from arts to literature,

Any building can last if it's taken care of.

The ideals of this architecture speak to monumentality,

Durability, but also democracy.

This building will stand for a long time,

And it is supported by the people.

Narrator: Though we don't know if our pantheon would stand

For 2,000 years,

We'll always need a place where people can come together

And share ideas.

The pantheon dream is to gather as a community under one roof,

United in the belief of what great things we can accomplish.

If we built it today.

But we're just getting started.

We'll host our first event, a symposium,

Featuring the world's pantheon of experts on ancient rome.

We did it!

We build a new pantheon in new york city.

It's made of 100% concrete.

It took 3 1/2 years and 350 people to do it.

So, how much did it cost?

We asked the team in toronto to crunch the numbers for us.

Maybe in the range of something like $170 million

To around $200 million itself.

Narrator: Let's put it at $200 million to build the structure.

All right, we're all set to roll again.

On top of that, there'd be additional costs

Such as land, development, permit fees.

The cost depends on finishes.

The cost depends on the ultimate use of the building.

Narrator: We'll add in another $100 million

To cover the cost of our luxurious interior work.

So, final price tag? $350 million.

But can we get a 2,000-year insurance policy?

If you were to put steel inside the concrete of the pantheon,

That steel or iron would corrode within a few centuries.

Narrator: Even if materials degrade over time,

To when you get the concrete into the form works.

And we're filling the forms with concrete now.

Narrator: We take the heavy-duty approach these days,

But it was the romans

Who conquered concrete construction first.

Andrews: They would have used like a timber box coming up.

They basically provide a void, in other words,

An opening for the concrete to sit into.

They would have poured concrete.

They would have slid the box up.

They would have poured concrete.

You would have to have it done in an efficient way

Because there's a time from when you mix the concrete

The steel -- reinforcing steel has been tied,

Narrator: Timing is everything, and at this construction site,

Work has ground to a halt.

Just bear with me a sec here. We gotta --

Man: Well, what's happening? This seems pretty bad right now.

Well, yeah.

The ppo shaft which what drives the hydraulics,

Which drives the drum, it just -- it let go,

So without that, we're not able to turn the drum.

So now we're not able to unload the concrete yet.

Not pretty right now.

Narrator: Time's ticking for kevin and his concrete crew,

So the pumping cylinders,

Fares: Whether you're building a skyscraper, a pyramid,

Or just a simple building,

I think there's some principles of studying the project,

Getting your right team onboard,

Getting your budget, and implementing.

Narrator: That's exactly what's happening here

At the job site of this $200 million development.

Kevin nickerson's team is in charge

Of supplying all of the concrete.

Nickerson: Just dumping the concrete into the back of the truck.

There are two large pumping cylinders,

And we've got problems of our own.

One, is actually sucking to fill the cylinder.

The other is pushing to empty the cylinder.

So as they come out, the concrete flows down through

What's called an s-pipe down here.

Concrete is sucked into one of the cylinders.

It switches over and pushes out, comes down through the pipeline,

All the way up through the boom, and then all the way to the end.

Narrator: The temporary shell where this concrete will set

And harden is called a form.

They've obviously got the form work, obviously, in place.

The forms are in place.

Which is basically a stairway.

Kevin's digging deep to get his big job back on track.

We're just trying to empty this out just enough

So we can get 'em back down the road.

With the drum not being able to turn, the concrete,

We've got about two hours, give or take,

And the concrete is going to get hard,

And we're not gonna be able to get it out of the drum.

So there's a bit of an emergency.

Narrator: With the mixer breaking down, the crew might have to resort

To ancient back-breaking building techniques,

Roman style.

They would have had to make scaffold around this,

Narrator: While we're waiting for the concrete to dry,

They would have to bring the concrete up in wagons

Or buckets or something like that.

Narrator: Good news.

Reinforcements have arrived.

We got two more trucks just arriving to the site.

They finally got through the traffic,

So we're rushing to get 'em backed in here

To keep things rolling again.

So we'll get him geared up.

[ metal creaks ] [ distant reverse beeping ]

And we got another one coming in right behind him.

Were secured to the rock.

Just how much is this all going to cost?

Narrator: We're imagining a 21st century convention center

Shaped like the pantheon, but twice as big.

This brutalist beauty will be made

Of the strongest concrete in the world,

And it's going to take up to 350 workers

3 1/2 years to build.

So, let's do it.

First up, our foundation.

Blackman: You would excavate the bedrock, install the footings,

Put rock anchors in so that the actual footings

On top of this, we can actually add pigments to give you

Narrator: Once the foundation's secure,

We'll erect the structural frame of our pantheon.

Andrews: There's six individual,

Large frame column systems that support the roof itself.

So what we would do, basically, is construct

The forms themselves.

It's a temporary structure.

We'd place rebar inside that.

The concrete would come in and be poured.

It would sit there for a day or two,

And then we'd release it and take the forms off.

And a community?

Our modern mega-developer loves the idea.

Whether you're building a structure 2,000 years ago

Like the pantheon or building a beautiful building today,

The same philosophy and culture and artistic flair

Should be reflected.

And that's why it's important to surround yourself

And your team with such creative minds

That reflect the day of that you're erecting a building.

Narrator: Sounds like a great idea,

But can we afford this architectural feat?

The question of profitability, it's a question mark for me.

But is that important if you're building a culture

In worship of this ancient roman temple?

In my view, that's secondary.

Narrator: We'll have to come up with the necessary funding

To complete our project,

But before we build our budget, we've got to figure out

What this building is gonna look like.

And what we're going to build it out of.

Ochsendorf: If we were to rebuild the pantheon today,

I would fight to build it out of traditional materials.

Narrator: But we don't exactly know why they built this pantheon.

And it wasn't even the first one.

Higgins: This is, in fact, the third pantheon on this site.

Mccallum: We're certainly capable of reconstructing

Over the past two millennia.

It's this amazing feat of architecture and engineering

That has lasted for so long, and you can visit it today,

And it's not much different than it was

When it was originally built.

Narrator: But could we build a long-lasting pantheon today?

When we build today, we often think in terms of decades --

Possibly a century.

Romans built for millennia.

In some respects, it's not really possible

Based simply on the material used, the concrete.

Roman concrete is quite different from today's concrete.

There were two other pantheons, and they both burned down.

The exact same forms,

Making a dome the same size, putting up columns out front.

All of those elements we have the engineering, skill,

And construction expertise to do.

I guess the question is, to what end?

Narrator: It's time to reimagine this architectural wonder.

Mccallum: We would want to go bigger than the pantheon.

We want something that is cutting edge,

That takes that to the extreme and is different than anything

That anybody has really seen or experienced to date.

Narrator: Can we build a modern engineering icon

Mccallum: If you think of it, it's a place where people came together.

Narrator: The legacy of the pantheon is on full display across the globe.

Ochsendorf: You see reading rooms, capital buildings,

Museums influenced by roman architecture

And particularly by the pantheon.

Narrator: Seven million people pass through the wooden doors

Of this ancient icon each year.

We wanna make sure our modern-day pantheon

Will also draw a crowd.

Narrator: Millions of tourists flock to the pantheon each year

To get a glimpse of ancient rome in all its glory.

In fact, people have been gathering at this iconic site

For thousands of years.

Or to provide a house for books or a house for government.

They met. They exchanged ideas about things.

We have all sorts of buildings

That fulfill the same function in the world today.

If you think of a trade and convention center.

Narrator: Like a convention center today,

The pantheon was a destination building

That brought the masses to the center of the city.

And our modern mega-developer believes that today,

If we build it, they will come.

We build world trade convention centers

And cultural centers these days.

A time when the role these temples served in roman life

And it's thought that probably the original temple here

Was dedicated to the olympian gods.

Mccallum: Roman temples, they're different in what we would conceive of,

Let's say, a church or a synagogue or a mosque

In which you worship in the interior of the building.

You go as a community during specific religious festivals,

So thousands of people go to attend these things,

And there's just not enough space inside the temple.

All of the ceremony takes place in the exterior.

Narrator: Pantheon version three was commissioned

By emperor hadrian in 117 b.C.

No building has played a more important role in roman life

Was evolving.

We think that probably this pantheon, the third pantheon,

Functioned more as a kind of audience hall for hadrian,

Rather than as an actual temple as such.

Narrator: Rome's pantheon has served as an ancient temple

For polytheistic worship, an emperor's private soap box,

And today, a christian church.

This dome's sure worn a lot of hats over the years.

We wanna re-create the pantheon today,

But what purpose will our structure have?

Today, we might build a pantheon to honor heroes

Most of the ancient metropolis has since fallen into ruins,

We would want to go bigger and do something

That is even more innovative.

Narrator: We're on the job site of one of the world's greatest wonders.

And we're wondering, how long would it take?

How much would it cost?

How many workers would we need?

Could we even do it if we built it today?

-- Captions by vitac -- www.Vitac.Com

Captions paid for by discovery communications

Narrator: Rome.

Italy's bustling modern capital.

2,000 years ago, it was the biggest city in the world.

We have to think in terms of millennia.

But the pantheon still stands.

Pantheon is one of the great mysteries

Of the roman world.

You don't have that many literary references

About the naming of the building.

The word pantheon means "of all the gods."

Ochsendorf: Its purpose, why exactly it was built the way it was,

It's really wrapped in a whole series of mysteries.

But one thing we can agree upon

Is that there are some unbelievably innovative

Construction methods in the pantheon.

That the romans used.

Has been drawing a crowd since it was built 2,000 years ago.

Higgins: I can't think of a place

That would give a greater sense of your power.

Narrator: It's the ancient romans' best-preserved building.

Made out of their most famous building material.

Using concrete, romans were able to expand

Into whole new geometries of construction.

They began to build large domes that had never before been seen

In the history of the world.

Narrator: As our concrete world crumbles around us,

Could the secret solution be hidden inside the pantheon?

Mccallum: Concrete we use today is different than the concrete

Narrator: It's 14 stories high.

The romans took what could have been a rather dull,

Utilitarian material,

And they turned it into what was really an art form.

Narrator: Can we do as the romans did and use concrete

To erect an architectural icon?

The same philosophy in cultural and artistic flair

Should be reflected.

Narrator: We're mixing up the strongest concrete on earth

And getting ready for a brutal battle

Between classic and contemporary.

Ochsendorf: If we were to rebuild the pantheon today,

Narrator: But as the sun began to set on the roman empire,

And the united states capitol building.

Today, it is still the largest unreinforced concrete

Building in the world.

Mccallum: It's this interesting domed --

Concrete dome structure above you,

And the hole in the roof, too, an oculus,

That lets in light to illuminate the interior.

Narrator: This opening to the skies remains uncovered to this day.

When it rains, water drains out through four tiny grates.

The whole purpose of the dome and the oculus

Was to represent the power of the empire

And the power of the single light source, the emperor.

It's bigger than the dome of st. Peter's cathedral

The pantheon's ownership changed hands.

In 609, it was changed into a christian church.

Ochsendorf: When the pantheon becomes a church,

It basically guarantees its survival

For the next 15 centuries

Because it becomes a living house of worship.

Higgins: Being a christian church means that it's being repaired.

It's being structurally supported.

Narrator: As a church, the pantheon has served as a final

Resting place of kings,

Queens, and the renaissance artist, raphael.

And statues.

Not much compared to today's most famous skyscrapers.

But the pantheon endures as a masterpiece

Of architectural beauty and engineering acumen.

If you were a roman coming to see this pantheon

For the first time,

What you would have seen as you walked towards it

Is a very conventional temple.

But hen, as you went inside,

It was not a conventional temple at all.

Everything about it was opulent.

Narrator: Today, it's adorned with renaissance-era paintings

It's to bring communities and cultures together.

But its marble floors and granite columns

Have been turning heads for thousands of years.

Only once you enter the interior space do you see

That the building is not rectangular.

It's circular.

Higgins: The height from the oculus to the ground

Is the same as the diameter.

Which means that, if you were to continue the dome,

You would have a perfect sphere.

Narrator: This dome is the pantheon's crowning achievement.

Built with more than 4,500 tons of roman concrete,

This is one of thousands of ready-mix concrete plants

Using volcanic ash from near mount vesuvius,

And they discovered that a particular ash was reactive,

Meaning that if it were ground into dust and mixed with water,

It would set hard and become essentially a liquid stone.

Narrator: The volcanic ash is called pozzolana,

But it's in scarce supply in our modern construction world.

Pozzolana isn't used so much these days

Because of difficulties of access, because of expense,

And because of limited supply

Compared to other materials that we might include instead.

Narrator: But can we use modern-day concrete to build our pantheon?

Well, let's find out.

Ochsendorf: The romans developed concrete

Spread across the world.

We've got kevin nickerson here to help us

Mix up the strongest concrete earth can provide.

Nickerson: We can give you as much you want

To whatever specification you need.

That specification might be color.

It might be texture.

So if you need it flowable, we can do that.

You need it durable, we can do that.

Narrator: Maximizing the strength, durability,

And even the aesthetic of concrete

A concrete pantheon should be no problem, right?

It was built in 1903.

It was only 16 stories high,

But it laid the ground for the modern concrete explosion.

The hoover dam was, by far, the biggest concrete structure

Ever built when it opened in 1936.

There's enough concrete here to pave a highway

From san francisco to new york.

Or build over 1,000 more domes for the pantheon.

Today, almost everything we build uses concrete.

It's a $35 billion industry in the usa.

The romans may have invented it,

But we've taken it to new heights.

Is all about the ingredients you use.

Narrator: 2,000 years ago, the roman pantheon

Was a pioneer of concrete construction.

We want to use the same material to build our modern-day replica.

But how does today's concrete measure up?

Mccallum: Roman concrete is different from the concrete that we use today.

Contemporary concrete is typically highly liquid.

Roman concrete is less liquid. It's more like a mortar.

Whatever structure we build may have the form of the pantheon,

But it's unlikely to have its durability.

Narrator: Most experts attribute roman concrete's exceptional strength

To a special ingredient inside its mixture.

And we'll quite commonly use that

A catchall term for the crushed stone,

Gravel, and sand used as reinforcement.

The stronger your aggregate, the stronger your concrete.

Nickerson: This is our main source of coarse aggregate.

In general, all concrete, the majority of the concrete,

Is gonna be done with the 20 mil or the 3/4-inch aggregate.

It's pretty straightforward.

This is what we'll call our 14-millimeter aggregate,

So a little bit smaller than the general, everyday stuff.

But it meets the needs of a decorative concrete, as well.

You can see, this one has some very distinct

Coloring properties -- kind of a reddish brown.

Now, ingredient number three, aggregate.

In an exposed aggregate application.

The difference -- main difference between the two

Other than the visual ones is, in fact,

This one is considerably more expensive than this one.

Narrator: We're willing to break the bank for a concrete

That really shines.

Quite often, I think many people think of concrete as gray

And dull and boring.

But with aggregates like these,

Well, we can make some very appealing-looking concretes.

There are yellow ones. There are black-and-white ones.

And softer rocks like shale or clay.

There's four basic components to concrete.

There's water.

There's aggregate.

Cement.

And there's add mixtures, chemical add mixtures.

So as long as those materials are available,

We can keep producing concrete to your heart's content.

Narrator: By far, the most important ingredient in concrete

Is cement.

Cement is made by grinding

And combining reactivity-prone rocks like limestone

The ingalls building in ohio was the first concrete skyscraper.

Superheat the mixture,

And you get a rock-hard chemical compound.

Grind it into a powder -- that's cement.

The cement is what forms the paste.

That ultimately is what gets hard and make concrete concrete.

Cement is to concrete basically as flour is to bread.

Narrator: Cement is the second-most-used resource in the world.

The first -- water.

Another ingredient in our recipe.

Together, water and cement

Form the glue that holds concrete together.

Narrator: Not only is this the biggest city in america,

In the history of the world prior to the 18th century.

Narrator: But it wasn't just its population

That made ancient rome the greatest city of its age.

Mccallum: It's crowded. It's busy.

It's always buzzing with activity.

It's also a cosmopolitan center.

Narrator: Rome 2,000 years ago sounds a lot

Like the biggest city of a modern superpower.

Robins: New york city must be the most dynamic city

Or one of the most dynamic cities,

Certainly, in the world,

And it's constantly changing and growing.

Which makes it larger than any city

It's among the most cosmopolitan cities in the world.

Robins: You know, the classic new yorker was born somewhere else,

Got to new york, looked around, and said,

"thank god I have found home."

Those of us that were born here, like me,

Are descended from people like that.

Narrator: More than 8 million people live in new york city.

And every year, almost 63 million more come to visit

Its temple of tourist attractions.

Robins: A place of beauty, a place of grand buildings,

A place of memory.

Where are we going to build?

I think by inviting people to come to your community

And the core and the heart of your city,

They spend time in your restaurants, in your hotels.

I mean, there's a cultural exchange.

Narrator: If we wanna use the pantheon as inspiration

To build a modern convention center,

We've gotta build something structurally sound,

Architecturally renowned,

And strong enough to last for at least 2,000 years.

And that mission will guide every decision

We make about our modern-day pantheon.

And also, I suspect that quite a few of the buildings

What are we building it out of?

What's it going to look like?

How are we going to do it?

How many people is it going to take?

How long?

And how much is this whole thing going to cost?

Before we bring in the heavy equipment,

We've gotta figure out where we're going to build it.

When this pantheon was built, rome was a super-sized city.

Mccallum: There were probably between 1 million and 1.2 million people

Who lived in the city,

It's likely not going to be identical to the original.

Neglect, and degradation.

But today's buildings come down with a bang.

The united states alone produces almost half a billion tons

Of construction and demolition waste a year.

Most of that debris, you guessed it, concrete.

So, do we really want a pantheon made from 21st century concrete?

As we think about building a monument that's going to last

For a millennia as the romans built,

We have to consider the durability

And the solidity of those materials.

Narrator: And even if we want to use concrete

For our modern-day pantheon,

Thanks to 1,500 years of pillaging,

One of the great inventions of the roman period

Was roman concrete.

They really made it into their own material

In a way that other cultures didn't.

With concrete, you can make shapes that curve,

And you can use it in bow vaults and arches

And domes to span huge distances.

Narrator: But with the fall of rome,

The recipe for concrete disappeared.

We wouldn't see large-scale concrete construction again

Until the dawn of the 20th century.

Used in the structure is concrete.

Going up right now that are so new come back in 30 years,

They'll be landmarks.

Narrator: So, we'll build in new york city.

But what are we going to build it from?

The search starts here.

The pantheon is made of a number of materials.

There are building stones used, travertine and limestone.

There are granite columns.

There are marble decorative elements.

Brick is used throughout, as well,

But the most important single building material

Narrator: The pantheon -- a temple to the mythical gods of ancient rome --

Narrator: But why doesn't the pantheon look anything

Like our modern concrete buildings?

The viewers at the time wouldn't see the concrete itself.

The concrete always had facing material on it,

So they see the facing material.

They don't see the concrete.

The problem with concrete is that,

Once you take off the facing material,

It becomes very susceptible to degradation.

And so it erodes away.

Narrator: The ruins that litter rome to this day fell apart gradually.