NARRATOR: The Colosseum-- the Roman Empire summed up in stone.

Never has such a civilized culture poured so much of its wealth into engineering spectacles of death for the entertainment of its people.

In the morning you had wild beast shows.

At around the lunchtime, crucifixions.

In the afternoon, the pièce de la résistance, two men, fighting to the death.

NARRATOR: Ancient Roman accounts document the Colosseum's repertoire in chilling detail.

They depict an orgy of outrageous spectacles-- costumed gladiators cast in battles to the death, exotic animals unleashed on unsuspecting victims, even sea battles with thousands of people killed.

Were the Romans as bloodthirsty in their theatrics as ancient authors report?

To investigate, a subterranean archaeologist explores tunnels beneath the Colosseum to discover how it could be flooded for naval battles.

A forensic scientist gives voice to gladiators whose battle-bruised bones bear witness to their own deaths.

FABIAN KANZ: We had in our hands for the first time remains of real gladiators.

NARRATOR: And an architect pieces together clues of an elaborate system of ancient special effects machines.

Then, with a team of engineers and builders, they reconstruct it, and for the first time in 1,500 years release an animal into the Colosseum.

Now, can scientists and scholars unlock the secrets of how and why the Romans engineered such bloody spectacles?

Right now on NOVA, "The Colosseum: Roman Death Trap."

If one building best symbolizes the gore, glory and genius of the Romans, it is the Colosseum.

It is a spectacle of design and engineering, the biggest building they ever constructed.

It spans nearly 2,000 feet around, soars over 160 feet high, and soon after it opened in the year 80, it was decorated in gleaming bronze shields and 16-foot statues of gods and heroes.

To this day, the Colosseum stands as a powerful landmark on the skyline of Rome.

When the Colosseum was built, it had an enormous effect because of its size, status and presence in Rome.

(crowd cheering) NARRATOR: The echo of its 50,000 spectators cheering bloody theatrics continues to haunt imaginations.

Gladiators fighting to the death, mass crucifixions, elaborate animal hunts.

Over four centuries, the Colosseum was witness to an estimated million human deaths.

And with up to 11,000 animals killed in a season, some species, like the Balkan lion and a North African elephant, were driven to extinction.

Yet the Colosseum was much more than a spectacular slaughterhouse.

It was a carefully engineered entertainment complex designed to reinforce Roman world order.

KATHERINE WELCH: Watching fighting on a regular basis for entertainment gave the Romans a sense of who they were and infused them with a kind of military ethos that was instrumental in creating and maintaining the empire.

NARRATOR: Ancient Roman authors, such as Martial in his Book of Spectacles, describe how that world order played out on the arena's stage.

They cast the emperor as master illusionist.

On his command a menagerie of ostriches, crocodiles, rhinos, bears and tigers magically appear to be dispatched by hunters.

A condemned criminal is dressed in wings and catapulted across the arena to play out a Greek myth.

And fantastical sea battles take place where thousands of prisoners of war are either slaughtered or drowned.

Can these astonishing accounts of elaborate executions be true?

Or has the boundary between history and myth been blurred over time?

Most recently the Colosseum was brought back to life in the film Gladiator, where tigers spring from out of nowhere to maul Russell Crowe.

But that's Hollywood effects.

The Romans were doing it for real.

Parts of the movie Gladiator are based on events portrayed in ancient texts and mosaics.

They depict gladiators locked in combat and wild beasts mauling people.

But none of these accounts describe how the Romans made these animals magically appear.

Some scholars suspect the secret may be hidden in the Colosseum's basement.

The hypogeum, the Greek word for "underground," is a maze of corridors and collapsed walls.

Architect Heinz Beste thinks that here, hidden from the spectators above, is where the Romans engineered their murderous magic.

(Beste speaking German) (translated): We have to imagine this being covered by the wooden arena floor above.

It was dark down here, lit only by torches and small lamps.

NARRATOR: Today, the arena floor has been partially rebuilt r tourists.

The original was made of wood and covered in sand to absorb blood.

The floor and all its wooden supports are long gone, but etched into the walls of the hypogeum Beste finds deep cuts and grooves.

To decipher these fossil-like remains, he drew every stone on every wall.

After more than two years, he began to make sense of the mysterious markings.

BESTE (translated): Through these drawings it was possible to connect these clues and turn the whole puzzle into a system that can be explained.

NARRATOR: Here he finds impressions made by wooden beams.

And evenly spaced along the floor are a series of round holes in concrete.

BESTE (translated): Here is another piece of the puzzle.

This is a base for a capstan.

NARRATOR: A capstan is a large round pole that could be turned by workers to lift something.

BESTE: Ah, interesting.

Up here we see an indentation for a ramp.

NARRATOR: Another mark reveals where a ramp might have led to the arena.

In Beste's mind, the pieces come together... Support framing from the floor of the hypogeum to the floor of the arena.

Halfway up, a horizontal beam for workers to stand on.

A capstan with poles for workers to turn.

A channel where a cage could fit.

And finally, a trap door that could lower to become a ramp leading to the arena floor.

Together they form what could be a device to lift and release animals.

(translated): I believe, given the evidence, there must have been an ancient lift system here.

NARRATOR: Throughout the hypogeum, Beste finds evidence of ancient backstage machinery, a total of 28 lifts.

Has Heinz Beste discovered the secret to how the Romans made wild animals magically appear in the arena?

To find out, he wants to construct a lift and trap door system-- install it right here in the Colosseum and raise an animal into the most famous amphitheater on earth.

But why did the Romans build the Colosseum to stage these bloody spectacles?

Part of the answer is hiding in plain sight.

For years, a cast aside stone was used as a place for visitors to rest, its importance completely unnoticed.

In the 1800s, an inscription was discovered on its surface.

It ended up here in the Colosseum museum, where it became, once again, largely unnoticed.

But hidden beneath these 5th century letters may be another, much earlier inscription.

Rosella Rea is director of the Colosseum and one of the leading experts on the building.

Mixed within the engraved letters she sees a series of strange holes.

(Rea speaking Italian) ROSELLA REA (translated): You can see with the naked eye that the holes are arranged in a regular pattern.

By studying their layout, it was found that the holes form a series of letters.

NARRATOR: The holes are where bronze letters had once been fastened to the stone.

(translated): This was the hole for the first letter.

The letter "I" for "imperator."

NARRATOR: Or "emperor."

Connecting all the dots reveals the original inscription.

The Emperor Vespasian ordered this new amphitheater to be constructed from the booty.

Vespasian Flavius becomes emperor in the year 69.

The following year he orders construction of the Colosseum to begin.

The stone is the plaque from its dedication.

And the letters spell out how the Colosseum was paid for, with booty.

But booty from where?

Vespasian's son left a clue on the nearby Arch of Titus.

On it, Katherine Welch finds depictions of Romans sacking the Temple in Jerusalem.

WELCH: One of the panels depicts the menorah, the Torah, and the sacred table, carried by elite young Roman men.

This is quintessential war booty, the things that meant the most to the people from whom they were seized.

NARRATOR: Following his son's conquest of Judea in the year 70, Vespasian is rich with gold and slaves.

He can build anything he wants.

So why the Colosseum?

Vespasian needs a building that makes a bold statement-- that he, Vespasian Flavius, is nothing like the emperor before him, the infamous Nero.

Emperor Nero's rule is marked by extravagance and much of Rome burning.

He confiscates land and builds a pleasure palace with gardens and a manmade lake.

Nero is driven from the throne, commits suicide, and Rome is engulfed in civil war.

WELCH: After a ghastly year of civil war and the suicide of Nero, Vespasian did everything in his living power to ingratiate himself with the Senate and consolidate his personal power.

NARRATOR: After fighting his way to the throne, Vespasian casts himself as the anti-Nero.

He buries Nero's palace, fills in his lake and on top builds the opposite of a pleasure garden-- a public building for blood sports.

WELCH: In building the largest, most expensive building in Rome, a building for popular entertainment, it celebrated military power and put it into a frightening, exciting, chastening context.

NARRATOR: The Colosseum is the perfect symbol for how Vespasian and Rome came to power.

And to enhance the blood sports, Vespasian builds in some deadly surprises, releasing wild animals into the arena.

But reconstructing the lift that could have done this is an audacious plan.

If Heinz Beste is to succeed, he'll need to find an ally on the inside.

Umberto Baruffaldi is an engineer, inventor and GoPro enthusiast.

He too is captivated by how the Romans released wild animals into the arena.

Umberto also happens to be director of health and safety for the Colosseum.

Beste shares his drawings with Umberto.

UMBERTO BARUFFALDI (translated): The drawing is beautiful, but how are we going to make it work?

NARRATOR: Beste's drawings provide a skeleton of the system, but it's not clear how the lift actually works.

Umberto brings in structural engineer Giovanni Squillacioti and material engineer Flavia Campanelli.

CAMPANELLI (translated): We have to create a system of pulleys and counterweights that works perfectly and synchronizes.

NARRATOR: Giovanni translates Beste's two-dimensional drawing into a three-dimensional computer model.

NARRATOR: The trap door is one of the big challenges.

On one hand it has to open to release the animal into the arena.

NARRATOR: But when it's closed, it has to support the weight of gladiators, charioteers and heavy animals trampling on it above.

Giovanni puts the pieces together and connects them in his computer model with pulleys, ropes and hinges.

Perfecto.

NARRATOR: Then, based on Giovanni's 3D wizardry, Heinz and Umberto build a scale model.

NARRATOR: At the heart of the system is the capstan, a large central pole.

As this is turned, it wraps a rope around it.

The animal is placed in this cage.

It's connected to the capstan through a series of pulleys, so as the capstan is turned, the cage rises.

Two large hinged arms support the trap door when it's closed, and then swing down to open it.

As the cage rises, the door automatically opens, releasing the animal onto the ramp.

BARUFFALDI (translated): The model is essential to experimental work of any kind, because it is the model that allows you to understand all the mechanics.

NARRATOR: And building the lift and trap door system will provide a window into a uniquely Roman pastime, in a uniquely Roman building, the amphitheater.

Mark Wilson Jones is an architect with an expertise in Greek and Roman buildings.

He's here in Arles in southern France, at an amphitheater constructed about 20 years after the Colosseum.

MARK WILSON JONES: In general, the Romans took their building forms from the Greeks.

But this is not the case for the amphitheater.

The amphitheater was a definite Roman invention.

And they created it for the special circumstances of gladiatorial fights.

NARRATOR: Amphi means "double" in Greek, and amphitheater translates as "double theater."

But if a Greek theater were just doubled, it would be round.

The Roman amphitheater is actually a stretched circle, or an oval.

Wilson Jones believes the Romans' innovation of the oval shape may be a direct result of the building's function-- a place for gladiator combat.

WILSON JONES: Most buildings are rectangular.

And that's a bad thing because you can get action stuck in the corner.

NARRATOR: If a gladiator gets stuck in a corner, he gets killed quickly.

The oval shape helps prolong the action for maximum entertainment value.

WILSON JONES: So this shape has a dynamic quality, no corners.

Everything's smooth.

So the action can move around.

And I think that really helps it maintain its excitement.

NARRATOR: An amphitheater for gladiator combat is uniquely Roman in form and function-- exactly the symbol Emperor Vespasian needs to project his power and inspire Roman pride.

WILSON JONES: There's this strong connection between the unique shape of the amphitheater and gladiatorial performances, the link with the military, the conquest of empire.

The great crowds of 50,000 that came together in the Colosseum were celebrating all of that.

It's really a sort of great day out to feel a Roman citizen and feel at the center of the world.

NARRATOR: In a forest northeast of Rome, Umberto is in search of the perfect tree for making the lift.

NARRATOR: The tree will be used for one of the key parts of the lift, the capstan.

NARRATOR: To fell the tree, the team uses the same tools as the ancient Romans: the ax, the two-man saw and a wedge.

Carmelo Malacrino, an expert on ancient Roman building, knows what tools to use from images on the Trajan Column, erected just 30 years after the opening of the Colosseum.

(translated): This column shows a fantastic series of tree cutting.

It depicts the deforestation process for constructing new roads and the creation of campsites as part of a military campaign.

NARRATOR: After an hour of chopping and sawing, the tree comes crashing down.

Now, the tree begins its transformation into the capstan.

But Umberto leaves a little bark as a reminder of where it came from.

The team uses their scale model as a guide for building the lift.

BARUFFALDI (translated): The move from the model to the real thing was a little traumatic.

Working in a dimension four times bigger really amplifies the problems.

NARRATOR: The cage itself will weigh over 800 pounds.

It needs to be strong to keep wild animals inside.

(translated): We have to pay attention to the sturdiness of the cage since it's supposed to hold lions and tigers.

NARRATOR: Seeing the lift at full scale, Umberto starts to have some concerns.

BARUFFALDI: The most difficult part will be getting the lift in without touching the Colosseum.

Because if we damage the Colosseum, I'll be chased out of the Colosseum.

NARRATOR: Today, the Colosseum is a majestic ruin.

Over the centuries, everything of value was stripped from its walls.

But coins minted for its opening and carvings on tombs show how the Colosseum was likely decorated.

In its arches stood 160 bronze statues 16 feet tall, representing gods and heroes the Romans borrow from the Greek pantheon.

At its top layer were gleaming bronze discs symbolizing captured shields.

Finally, framing the arches were columns of various architectural orders: Greek capitals on the upper three layers, but on the street level are Roman capitals.

WELCH: Vespasian is giving the people, the plebs Romana, exactly what they want-- Greek orders, Greek statues, but all with a Roman twist and pressed into the service of the conquering Roman state.

NARRATOR: The Colosseum's decorations amplify the message of the building's monumental scale: We Romans love Greek art and culture, but we have surpassed them.

Rome is the new superpower.

As a final touch, there was a bronze chariot above the entry arch on the north side, where the emperor could make his grand entrance.

But Vespasian will never walk beneath it.

He dies just months before the Colosseum is completed.

He does leave a lasting legacy though: the largest building in Rome and an imperial dynasty.

For the first time in Roman history, an emperor is directly succeeded by his natural son.

In the year 80, Titus holds the inaugural games in honor of his father.

Roman author Martial in his "Liber Spectaculorum"-- the Book of Spectacles-- describes the inaugural games.

A hundred days of crucifixions, wild beast shows, gladiator combat and, for the first time, the acting out of Greek myths with elaborate scenery and actual death.

WELCH: What happened with the inauguration of the Colosseum is that these Greek mythological executions entered the arena repertoire.

Except in the theater they were bloodless, they were just actors.

In the amphitheater they were condemned criminals who were forced to dress up as Greek mythological characters and killed in the Colosseum.

NARRATOR: The Romans would reenact well-known Greek myths, such as Icarus flying too close to the sun and falling to earth.

But in the Colosseum, there was a gruesome twist.

The criminal playing Icarus would be catapulted across the arena to his death.

This is not a myth.

It's real.

NARRATOR: Martial goes on to describe a mass execution so cruelly choreographed it surpasses even Roman standards.

Naumachiae-- mock sea battles where ships are sunk with hundreds of prisoners on board.

What astonishes Martial is not the mass murder by drowning, but rather how it was pulled off.

How could the Colosseum be flooded for sea battles in the morning, then drained quickly enough for gladiator combat in the afternoon?

The Romans were masters of moving water.

A network of 11 aqueducts carried clean water to Rome from mountain springs, some over 50 miles away.

The aqueducts provide the means to get water into the Colosseum.

And new discoveries are revealing a system to get water out.

Adriano Morabito, director of Subterranean Rome, has spent ten years mapping the city's underground water system.

One day while surveying for a new metro line, he took an unexpected turn.

MORABITO: We were mapping all the sewage system and suddenly we went into an older drainage system and we saw light at the end.

NARRATOR: To his great surprise, the light at the end of the tunnel was the Colosseum.

Morabito had stumbled into an ancient drain or "collector."

MORABITO: This is the only collector still working today.

In ancient times we had all four collectors getting rid of the water out of the monument.

NARRATOR: Beneath the arena, Morabito finds evidence of four drains that emptied water from the Colosseum.

And climbing to the top of the hypogeum, Morabito finds 40 channels that may have fed water in.

MORABITO: Some archaeologists speculate that this could have been used to flood the arena.

NARRATOR: Morabito believes the 40 input channels and four drains provide the plumbing to stage naval battles.

To put his theory to the test, he investigates how much water the Romans would need to flood the arena.

He finds four passageways leading into the hypogeum, wide enough to launch flat-bottomed boats into the arena.

MORABITO: When the arena was flooded the water was coming in here and then the boats were starting floating up to this level, because otherwise the water would have gone into other rooms.

NARRATOR: Morabito reasons the water could have been no higher than about five feet or it would spill over into other areas of the Colosseum.

Multiplying that depth by the area of the arena, he calculates, with the floor removed it can hold a million and a quarter gallons of water, equal to about two Olympic swimming pools.

But can the drains empty that much water fast enough to stage sea battles and gladiator fights all in one day, as author Martial describes?

(thunder) One night a thunderstorm puts Morabito's theory and the surviving drain to the test.

The storm dumps 800,000 gallons of water into the Colosseum, filling the hypogeum halfway.

That rainwater, with just one drain, empties in under two hours.

Morabito calculates that with all four drains working, the Colosseum could be emptied in less than an hour.

It was therefore technically possible for the emperor's engineers to flood the arena for its opening games.

NARRATOR: Morabito believes the Romans had the plumbing and enough water to stage mock sea battles in the Colosseum, just as the ancient texts claim.

But could they really lift animals into the arena?

After months of constructing the lift and trap door system in the workshop outside of Rome, today the pieces finally arrive.

The 440-pound trap door, the 2,000-pound frame and nearly 1,000-pound cage.

And the capstan, weighing in at 500 pounds.

Originally the pieces were built right into the walls of the hypogeum.

But today those fragile walls are a part of a protected World Heritage site that can't be altered.

So their idea is to pre-assemble the lift outside the Colosseum and then drop it into place as one self-contained unit.

SQUILLACIOTI (translated): Assembling the lift is a tricky process, almost as tricky as the design.

It's big and bulky.

And then lowering into the Colosseum is the most difficult part.

NARRATOR: Umberto has hired a 200-foot crane for this delicate operation.

Giovanni Cirillo is behind the controls.

CIRILLO (translated): The only issue today is the wind.

And the later it gets in the afternoon the windier it gets.

That might shake the structure and make my job less exact.

NARRATOR: After hours of assembling, the team is finally ready to raise the lift.

The crane hauls the machine to a standing position, and then... stops.

NARRATOR: There's a problem.

The crane has a built-in scale, and Cirillo discovers the lift is too heavy.

CIRILLO (translated): The load is 600 kilos overweight.

Over this distance that's a problem.

NARRATOR: The crane has the power to raise the lift, but when its arm extends out over the Colosseum, too much weight could cause the crane to tip over.

BARUFFALDI (translated): We don't know if we can get the lift inside.

The main issue is the crane might topple over.

NARRATOR: The team does some quick math to try to save the project.

SQUILLACIOTI: According to our calculations, the cage weighs around 450 kilos.

Once we take that away, the load will be lighter for the crane.

NARRATOR: They remove the cage, but they're still 150 kilos-- or about 300 pounds-- over.

Umberto confers with Cirillo and takes a calculated risk.

He green-lights the raising of the lift.

The crane hauls the lift up, nearly 200 feet and over the walls of the Colosseum.

Umberto holds his breath as the crane's arm stretches out over the hypogeum.

This shifts the crane's center of gravity.

If the lift is still too heavy, the crane could topple over, crashing into the Colosseum and smashing the lift into the hypogeum.

To make it even more challenging, Cirillo has to maneuver the lift without even being able to see it, guided only by radio contact.

Rosella Rea, director of the Colosseum and perhaps the person with the most riding on the success or failure of the lift project, arrives at the critical moment, as the team steers the lift between the narrow, fragile walls of the hypogeum with almost no wiggle room.

To everyone's immense relief, the lift slides in perfectly.

After flying the three-ton lift into place, the half-ton cage is a breeze.

BESTE (translated): Well, when you look at it as a drawing, when you imagine it in your mind's eye, or when you write about it, that's one thing.

But then to see it full scale, and to really be able to touch it, that's a whole other thing.

It's really amazing, and for me it's especially fantastic.

NARRATOR: With the lift in place, the team pops the Prosecco.

But they may be celebrating too soon.

They still have to turn all these parts into a working machine.

But why did the ancient Romans go to such lengths to make death theatrical?

Some answers are coming from the victims themselves, or at least their bones.

In 1993, Austrian archaeologists uncovered a cemetery in a Roman city in what is today Turkey.

Fabian Kanz of the Medical University of Vienna was brought in to analyze the human remains.

KANZ: It was a mass grave.

We found the remains from 68 people.

And 66 have been young males, aged between 20 and 30.

NARRATOR: Unusual injuries offer a clue to who was buried here.

KANZ: The distance is about five centimeters.

NARRATOR: These holes in the head, surely the cause of death, were almost certainly the result of a trident-- a weapon unique to gladiator combat.

The Roman author Suetonius describes seven gladiator characters, each with different costumes and weapons.

Onof the most famous pairings is a Secutor, equipped with a short sword, shield and helmet; and a Retiarius, "the fisherman," who fought with a net and trident.

From the forensic evidence, it's obvious who won this battle.

KANZ: It was the first known gladiator cemetery.

We had in our hands for the first time remains of real gladiators.

NARRATOR: Among many of the gladiator bones, Kanz finds something even more remarkable-- evidence of healing.

KANZ: What was quite surprising for us was the high number of well-healed injuries, which indicates there must be excellent health care for these gladiators.

NARRATOR: Ancient Roman texts offer a clue to one possible treatment, a special potion made from ash.

KANZ: And this might have been leaving traces in the bones.

NARRATOR: To find out if there's any truth to this gladiator potion, Kanz grinds a bone sample into a powder and processes it into a liquid that he puts into an instrument called an emission spectroter.

Here he sprays the liquid into an argon gas torch, where it burns with a distinctive flame.

The color of the flame changes, depending on the elements in the liquid.

And therefore, we can find out about the mineral composition of the bone.

NARRATOR: The flame turns from blue to a bright yellow, indicating that the gladiator bone has a high concentration of strontium.

Strontium is a natural element with properties similar to calcium, a crucial mineral for building strong bones.

It was mentioned in the historic texts that a kind of ash drink was substituted to the gladiators to remedy their pain after fighting.

And this would perfectly fit to explain this high strontium content of the gladiators.

NARRATOR: Kanz believes gladiators were given the Roman equivalent of calcium supplements to strengthen their bones.

But why go to this trouble to save gladiators?

Although slaves, gladiators were trained in special fight schools.

The remains of one, the Ludis Magnus, are right in the shadow of the Colosseum.

KANZ: The gladiators have been a big investment for the owner of the gladiator school, comparable to modern football or soccer teams.

And they wanted to save their investment.

And therefore, they engaged the best available doctors at the time.

NARRATOR: It would have been extremely expensive if half the gladiators were killed at every event.

To protect their investment, the Romans began to provide gladiators with medical care, so they could live to fight another battle.

And perhaps to compensate the audience for a reduction in the number of deaths, the emperor added entertainment value by ordering more elaborate stagecraft.

Now, all the major parts of the lift are in place: the cage, capstan and trap door.

BARUFFALDI (translated): Now that it's in place, we have to make it work.

The first task is installing all the missing pieces.

NARRATOR: They place wheels on the cage... handles on the capstan... and above the capstan, Umberto and Tullio install a spool for rope.

BARUFFALDI: We attach this rope here and as it turns, the rope wraps around it and pulls the cage up.

NARRATOR: The team connects the capstan to the cage with enough rope to stretch the length of two football fields.

Their earlier model is starting to feel very small indeed.

(translated): We only tested the model.

That was just 50 kilograms.

The real thing is 3,200 kilograms.

So that's why things are a bit tense here.

NARRATOR: With everything strung up, Umberto gives the lift a trial run.

He tries to turn the capstan without success.

The cage goes nowhere.

(translated): Three of us tried to lift it, but it didn't budge.

Not a bit.

It looked like an elephant.

Impossible to move.

NARRATOR: Umberto calls in reinforcements.

Even with six people, they can't turn the capstan to lift the cage or move the trap door.

It's all too heavy.

(translated): The ramp is very heavy and the lever system we initially designed does not work.

NARRATOR: How did the ancient Romans manage to lift so much weight?

(translated): We are facing the same challenges that the Romans had when they were originally making it.

The size is the same, the mechanisms are the same, and the problem is just as big.

NARRATOR: Umberto searches for a solution in an unexpected place: Roman ships.

Could the same mechanics that hoisted the heavy sails be used to lift the cage?

Umberto's hard drives are filled with images he's collected of surviving pieces of Roman ships.

Among them he finds what may be the key to heavy lifting, a simple device that dates far back in antiquity-- the pulley.

The cage weighs 800 pounds.

Adding a pulley splits the weight evenly between the two sides of the rope.

Another pulley changes the direction of the force.

It's easier to pull down than up.

With one pulley attached to the cage, it feels half the weight, only 400 pounds.

Attaching two pulleys on the cage makes it feel like only 200 pounds.

The more pulleys you add, the more the weight is distributed between them and the less force you need to lift the cage.

BARUFFALDI: The more I worked on this, the more I realized how great the Romans were, and how small we are in comparison.

Building the lift, I realized I was learning from them.

Learning directly from the ancient Romans.

NARRATOR: The team adds pulleys to redistribute the weight of the cage and trap door.

Umberto gathers eight men.

As they push the capstan, the rope glides through a network of 12 pulleys.

And the cage lifts up off the ground.

SQUILLACIOTI: The fascinating part is seeing this mechanism, which at first was essentially a static, seemingly simple structure, turn into something dynamic, a machine, simply by using these ropes, pulleys and human strength.

NARRATOR: But can this machine perform the Colosseum's signature magic trick?

To find out, the team wants to release an animal into the world's most famous amphitheater for the first time in 1,500 years.

But which animal?

According to legend, Romulus and Remus, the founders of Rome, were suckled by a wolf.

So a wolf is the perfect animal to test the lift.

Paolo Caldora rescues wolves taken as pets and then illegally abandoned.

He leads a wolf through the labyrinth of the hypogeum.

In ancient times, wild beasts would have been carried in already in cages.

The cage door is lowered, and the men turn the capstan to raise the wolf.

Every part is now working as a synchronized machine.

The trap door is lowered.

The cage rises into place, its door opens, and the wolf emerges into the arena.

(echoes of cheering crowd) The days of wild beasts in the Colosseum as hunters or hunted are thankfully long gone, and the wolf runs safely to his rescuer.

(applause) Heinz, Umberto and their team have not only re-created an ancient Roman lift machine, they have created a time machine.

For a brief moment, raising the wolf opens a window onto the spectacles here in the Colosseum 2,000 years ago.

BESTE (translated): Imagine not just one lift here, but a whole row of them, one behind the other.

The corridor was packed with lifts, which produced the spectacular action above.

Now, with the full-scale lift we can begin to get a sense of just how magnificent the stagecraft must have been.

It's really fantastic.

NARRATOR: Each year, over five million tourists visit the Colosseum.

They are awed by its size and horrified imagining the slaughter.

How could a culture as advanced as Rome justify the spectacular bloodshed that took place here?

WELCH: Gladiatorial games and associated violent spectacles needed absolutely no justification.

And in the ancient sources, we find just the opposite, that they were believed to stiffen moral fiber.

NARRATOR: Romans attending the Colosseum were more than spectators, they were participants.

These games showcased the power of Rome and reminded citizens that their prosperity was paid for in blood.

WILSON JONES: Inside the Colosseum you have spectacle, you have energy, you have entertainment.

The whole building is used as a vehicle for the demonstration of the power of the Roman world and how it came to benefit the populace.

NARRATOR: Though Rome falls to the barbarians in 476, the Colosseum, like a victorious gladiator, still stands.

Battered and triumphant, it is a lasting reminder of the gore and the glory of Rome.

The story continues online, A place of wealth and power.

The envy of the ancient world.

NOVA investigates... MAN: How were these facades carved?

What ancient technology transformed desert into an oasis?

And why did its people suddenly vanish?

"Petra: Lost City of Stone," next time on NOVA.

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