NARRATOR: It's one of the most magnificent cities of the ancient world: Petra.

Its monumental temple-like tombs soar over 100 feet tall.

And these wonders of engineering are not constructed; they're carved out of sandstone cliffs.

At its height, Petra was the center of a vast trading network in frankincense and myrrh and home to over 30,000 people in one of the most bone-dry deserts on earth.

UELI BELLWALD: It's not an appropriate location for a city.

There is not even drinking water down there.

NARRATOR: How did an ancient people supply enough water for this vast city?

And how did they carve these magnificent structures so high up in these cliffs?

To find out, a geoscientist teams up with stonemasons to carve a Petra-style tomb.

TOM PARADISE: We're looking at something that hasn't been witnessed for almost 2,000 years.

NARRATOR: And archaeologists and hydro-engineers discover how a group of nomads transformed this desert city into an oasis, the Las Vegas of the ancient world.

LEIGH-ANN BEDAL: It's really conspicuous consumption of this precious resource, water, in this desert environment.

NARRATOR: Finally, after 2,000 years, the secrets of Petra are about to be revealed.

Up now on NOVA, "Petra: Lost City of Stone."

NARRATOR: It's one of the driest places on Earth.

(camel grunting) Yet concealed among the canyons of this harsh desert in the Kingdom of Jordan is a magnificent ancient city: Petra.

For over a thousand years, its location remained hidden, protected by fortress-like cliffs and Bedouin tribes who fiercely guarded its secret.

Then, in 1812, a Swiss adventurer disguised as an Arab pilgrim risks his life to search for the legendary city.

Johann Ludwig Burckhardt makes his way through the Siq, a dramatic canyon rising almost 600 feet that twists and turns for nearly a mile.

Near its end, the canyon widens to reveal a towering temple-like facade.

It is called the Treasury, or "Khazneh" in Arabic.

Built 2,000 years ago, it is a masterpiece of design and engineering.

Majestic columns rise from the canyon floor, topped by ornately carved capitals.

Statues of mythological figures adorn its facade.

A fanciful urn graces its roof.

And a towering doorway leads inside to a room with three chambers.

Here, there is no elaborate carving, just the simple, natural beauty of the stone.

And then we back away and we realize not only is this building unique and fantastic, but it has been carved into the sheer face of living rock.

NARRATOR: The Treasury is actually a sculpture on a monumental scale.

At 80 feet wide and 127 feet tall, it is twice the height of the Mt.

Rushmore memorial.

As Burckhardt continues through the canyon, he discovers hundreds of magnificently carved facades everywhere, many rivaling the grandeur of Egypt, Greece, and Rome.

But there is more: the ruins of an entire city.

A 6,000-seat theater carved right out of the sandstone, a main street lined with huge temple-like structures, and even more spectacular monuments carved higher in the mountains.

But Burckhardt's rediscovery of the legendary city sparks more questions than answers.

Who built Petra, and why?

Burckhardt was inspired by stories of a mysterious desert tribe who gained their wealth trading spices and silks among China, India, Egypt, and Rome, and then hid their treasures of gold in the cliffs.

Greek and Roman sources provide a name for these people: the Nabataeans.

An account from the 4th century BCE describes the Nabataeans as nomadic tent-dwellers.

But three centuries later, another source describes them as a sophisticated people inhabiting a prosperous city.

Around the time of Jesus, Nabataea is a thriving kingdom surrounded by Egypt, Judea, and the vast North Arabian Desert.

How, in just a few centuries, did a village of tents become a wealthy kingdom?

And how, in the middle of a desert, did they build Petra?

Tom Paradise has spent over three decades trying to find out.

He is a geoscientist who specializes in preserving ancient structures.

Alongside the Treasury, he sees strange square marks that could be a clue to how it was built.

Are these marks the remnants of where an ancient scaffold was anchored to the cliff face?

PARADISE: For many years, people considered these to be holds for wooden scaffolding that may have been used for the actual carving.

NARRATOR: But Paradise has doubts.

If these are scaffolding marks, why did the Nabataeans leave them here?

And why are they found nowhere else in Petra?

Paradise believes the real reason for the marks may be tied to the fanciful name given to this monument centuries ago.

PARADISE: This building is called the Khazneh, it is the Treasury, and so legend goes back millennia that this housed riches.

NARRATOR: Because it is known as the Treasury, people have searched it for treasure.

Bullet holes riddle the urn at the top, and these marks may be footholds to climb up and get a closer look.

We think maybe those footholds were carved for the purpose of raiding the upper parts of the Khazneh looking for the treasure.

NARRATOR: But the urn holds no gold; it's solid rock.

The only treasures here are the magnificent sculptures.

Whatever the true purpose of these marks, Paradise is certain they're not for scaffolding.

After all, in this desert, wood is relatively scarce.

So how on earth could the ancient Nabataeans carve such a huge monument so high up in the cliff face without scaffolding?

Paradise has a bold plan to find out.

That go all the way down to the top... NARRATOR: Working with a team of stonemasons, they will try to carve a Nabataean-style facade for the first time in 2,000 years.

PARADISE: I may be sitting on the answer to the age-old question as to how were these facades carved.

NARRATOR: At the same time, archaeologists and hydro-engineers are investigating how the Nabataeans could even survive in this bone-dry environment.

BELLWALD: The entire hydraulic infrastructure was built, as I think I may prove, following one master plan.

NARRATOR: Their groundbreaking discoveries are revealing the engineers of Petra were not only masters of stone, but also of water, transforming a desert city into the Las Vegas of the ancient world.

Now, can scientists finally uncover how a nomadic tribe built this city of stone, and why Petra ultimately vanished into legend?

("Indiana Jones" theme playing) NARRATOR: Most people will recognize the Treasury from the climactic scene of Indiana Jones and the Last Crusade, where Harrison Ford and Sean Connery enter a secret temple to discover the Holy Grail.

But despite the great Hollywood story, the Treasury and most of Petra's iconic buildings are not temples; they're tombs.

The Nabataeans left very little writing, but on some of their facades are inscriptions in an Aramaic script, the common language of the Middle East in the time of Jesus.

This one, on a facade called Turkmeniya, reads in part, "This tomb is sacred.

"Nothing of all that is inside shall be changed or removed forever."

Tomb raiders disregarded notices like this, so human remains and grave goods rarely survive.

But body-sized niches leave no doubt these were burial chambers.

In all, the cliffs of Petra hold over 800 tombs.

CHRISTOPHER TUTTLE: The prominence of these monuments led many of the early explorers to consider the possibility that this might just be a city of the dead, a necropolis.

But over the past 200 years, all of the research has actually shown it was a city of the living as well.

NARRATOR: Chris Tuttle has been working here for more than ten years.

Although less than two percent of the site has been excavated, archaeologists have mapped and surveyed the area.

All in all, ancient Petra was a metropolis about the size of the island of Manhattan.

There is a two-square-mile downtown where people lived, worked, and prayed.

Suburbs housing more people stretch to the north and south.

Based on these surveys, Tuttle can estimate the population.

TUTTLE: At its height, we expect this city housed somewhere between 20,000 or 30,000 people.

NARRATOR: Yet unlike cultures that bury their dead in isolated areas, in Petra, tombs are everywhere.

Why did the Nabataeans carve their tombs throughout the city?

And how did they do it?

Paradise hopes his carving project will provide some answers.

PARADISE: Creating an experiment in which we reconstruct a facade will give us insight into how the Nabataeans carved these fantastic facades 2,000 years ago.

NARRATOR: But Paradise can't carve his facade here.

Petra is a protected World Heritage site.

He must find a cliff face with the right kind of sandstone somewhere else.

His search takes him a world away, to Southern California.

NATHAN HUNT: This looks like a promising prospect.

NARRATOR: While the ocean view is a sharp contrast to the Jordanian desert, the sandstone is identical to Petra's.

Paradise enlists stonemasons Blake Rankin and Nathan Hunt.

With permission from the landowner, they search for just the right rock.

Hunt is a classically trained master carver and architectural sculptor with over 18 years of experience.

We're looking for a fine-grained sandstone which lends itself to ornamental carving.

NARRATOR: Sandstone is a soft rock made of compressed layers of sand and minerals.

RANKIN: That looks like the type of stone we're looking for.

Yeah, this is great.

It looks like it's going to carve really well.

NARRATOR: The team has found the perfect rock and cliff face.

Now, they must find the right tools for the job.

Back in Petra, Paradise discovers a clue in the stone: chisel marks made from iron tools.

PARADISE: The technologies used with chisels in stonework haven't changed in 2,000 years.

We use the same chisels, and so they leave the same marks.

NARRATOR: By matching modern day tool marks with those found in Petra, their adviser Tom Paradise tells them exactly which tools to use: the claw chisel, the flat chisel, and the pointed chisel.

PARADISE: The pointed chisel is used for the coarser chiseling that removes large amounts of rock.

NARRATOR: So the pointed chisel is exactly what Hunt and Rankin use to begin work.

RANKIN: Yeah!

It feels good to be carving.

NARRATOR: But their exuberance fades fast.

Carving by hand is seriously slow.

HUNT: There's no way we can do it by hand.

NARRATOR: A Greek source says the Nabataeans had few slaves, but they probably did have plenty of skilled manpower and time.

Hunt and Rankin have neither, but they have power tools.

Even so, Rankin insists they're not cheating.

RANKIN: This is a chisel very similar to one that the Nabataeans would have used.

The only difference is that we've mechanized the hammer process so that we can move a lot of stone really quickly.

NARRATOR: The carvers have found the right rock and the right tools for the job.

As Hunt and Rankin prepare the cliff face, Paradise must decide what exactly to carve.

What makes a Nabataean tomb Nabataean?

Many of the facades in Petra actually look like they belong somewhere else.

At the Treasury, Paradise finds statues, columns, and capitals reminiscent of ancient Greece and Rome.

And across Petra, he finds architectural features from other far-flung empires: a step design associated with Assyria and Mesopotamia, elephant-headed capitals evoking India, even Egyptian obelisks.

But among the familiar are designs Paradise has seen nowhere else.

PARADISE: There's a pediment at the top that is split in the middle, capped by a cone, a capital, and an urn at the top.

This isn't Greek, this isn't Roman.

NARRATOR: This new design is seamlessly mixed with features from far-off cultures.

PARADISE: The architecture is this synthesis.

And this begins to tell us a story that is the real Petra.

NARRATOR: What makes a Nabataean tomb Nabataean is the combining of their own unique style with designs from other empires.

But how did these people in the middle of the desert come into contact with such faraway places?

Two words: frankincense and myrrh.

Frankincense and myrrh were must-have luxury items in antiquity.

In the New Testament, they are among the gifts the Three Kings bring to the baby Jesus.

Made from dried sap from trees in the southern Arabian peninsula, they were burned obsessively in religious ceremonies in Egypt, Greece, and Rome.

But to get that incense to consumers throhout the Mediterranean, it first had to be transported through the desert.

After centuries of living as nomads, the Nabataeans knew every secret source of water.

If you wanted to cross the desert and make it out alive, you had better have a Nabataean leading the way.

(camel grunting) Along the route, they built outposts to guard their goods and extract a toll.

In a valley just over the mountain from Petra, Andrew Smith has excavated this fort called Bir Madhkhur.

ANDREW SMITH: There was definitely a Nabataean presence here, most likely related to the trade that came out of Petra.

NARRATOR: Among the artifacts he excavated are dozens of tiny clay perfume bottles.

The Nabataeans were most likely processing some of the raw frankincense, and they would have bottled and then packed them tightly so that they weren't going to break and probably loaded them on camels or even donkeys.

NARRATOR: The Incense Road became the lifeblood of the Nabataeans, pulsing from Saudi Arabia to the port of Gaza, the gateway to Greece and Rome.

The financial reward from this trade catapults a desert tribe into a powerful kingdom.

Nabataean towns and tombs spring up throughout the northwestern Arabian peninsula.

By the first century, the Roman writer Pliny called the Nabataeans "the richest race on earth."

Much of their wealth went into building their capital city, Petra.

Tom Paradise believes the Nabataeans' far flung trade connections influenced their domestic designs.

PARADISE: Because Petra is a crossroads for the region, it makes sense that they would adopt and adapt different architectural styles from a lot of their trading partners.

NARRATOR: But with all these different styles, what should Paradise pick for his carving experiment?

PARADISE: This sort of facade represents more than 500 other facades in Petra.

So this style really is the archetype of the tomb facades.

NARRATOR: To Paradise, this tomb is typically Nabataean.

Although it appears plain, it's a mash-up of different architectural styles.

It has the remains of a Greco-Roman doorway, Nabataean capitals, an Egyptian cornice, and a design from Assyria that may represent a stairway to heaven, called a crow step.

But when the carving team transfers the design to California, it isn't wide enough to fit the rock.

You never really know how it's going to work in the stone until you get started.

We think it's going to look a lot better if we widen the facade.

NARRATOR: But how will making the facade wider affect the design?

Make each block of the crow step seven by seven inch.

This would be the edge of the crow steps.

RANKIN: That would be great.

NARRATOR: Grappling with this problem, the team may shed light on a mystery that has confounded scholars for decades.

Why do Nabataean tbs, while similar, have unique variations?

PARADISE: There is one motif they modify a lot, and that is the crow step.

Why the difference we have never really understood.

NARRATOR: Some of the tombs in Petra have crow steps that reach all the way down to a narrow ledge called the cornice.

Other crow steps meet in the middle.

Some scholars have argued this reflects an evolution in design.

But Paradise thinks they have struck upon a practical reason.

As we make the facade wider, it really requires us to take the crow steps all the way down to the cornice.

NARRATOR: If the facade is wider, the crow steps must break apart.

PARADISE: Increasingly, we notice that changes of the rock actually caused changes within the design elements.

I think we have to give more credit to the rock than we have in the past.

Just sort of roughly mark nine inches on there.

NARRATOR: By carving their own facade, they discover a basic principle of Petra: the rock influences what they carve and where they carve it.

But why here?

Choosing to build their capital in the middle of a rocky desert poses another age old question: how did the Nabataeans get enough water to support such a magnificent city?

One clue is here, in the city center, at a structure known as the Great Temple.

Its monumental stairway leads to a large stone platform surrounded by over a hundred columns.

Holes in the courtyard show there are channels running underneath it.

It's running under the floor.

SUE ALCOCK: Oh, that'll do it.

NARRATOR: Sue Alcock leads a team from Brown University to investigate.

ALCOCK: If we could make all this surface architecture go away, you know, just kind of magically lift it up and look down, I think we would see quite a network of these channels and canals.

NARRATOR: She may be sho on magic, but Alcock does have another way to look below the surface: a technology called GPR-- ground-penetrating radar.

TOMMY URBAN: Excavation is inherently destructive.

This is a way to get a look at what's down there in the same way you would go in for an x-ray perhaps before you went in for a surgery.

NARRATOR: The radar sends a high-frequency radio wave into the ground.

When the wave passes through different materials, like from stone to soil, part of the wave is reflected back.

But the speed of the wave changes depending on the material: slower for soil, faster through air.

Detecting these changes is how the GPR sees where the channels are.

The team systematically drags the radar back and forth across the courtyard.

URBAN: There's some kind of a channel right there.

ALCOCK: Oh yeah, look at that.

NARRATOR: Beneath the Great Temple is a network of channels that looks like plumbing.

Intriguingly, the channels seem to extend beyond the courtyard.

ALCOCK: When we look at Petra, we often tend to think about building by building, and actually, I think it was all tied together.

NARRATOR: Alcock believes these channels are evidence of a massive city-wide water system.

Petra was an urban center, and it had urban water supply.

NARRATOR: There's just one problem with this theory.

Petra is in one of the driest places on the planet.

If the Great Temple is indeed the heart of a vast engineering system that supplied an entire city with water, where is all that water coming from?

One possible source is still used daily by locals.

It's called Ain Musa, or the spring of Moses.

Allison Mickel and Cecelia Feldman of Brown University's survey team join hydro-engineer Charles Ortloff to investigate.

CECELIA FELDMAN: In Numbers 20:11, it talks about how the Israelites were wandering in the desert.

And Moses strikes this rock in anger, and water flows forth.

NARRATOR: The story of Moses miraculously bringing forth water has been linked in legend to this rock and spring.

But it would take an engineering miracle to get this water from Ain Musa to Petra's city center-- it's five miles away.

In the Siq, the entrance to Petra, the team finds evidence for how the water may have been brought here.

Running along the side of the path is a narrow channel which has imprints of what were once enclosed ceramic pipes.

CHARLES ORTLOFF: If you look inside of the channel, you can see the actual imprints of ceramic sections that are roughly about a third of a meter long.

NARRATOR: At roughly a foot long, it would require tens of thousands of segments to create a five-mile pipeline from Ain Musa, high in the mountains.

And every one of those joints would have the potential to spring a leak.

Could the Nabataeans possibly have pulled off such a feat of hydro-engineering?

At California State University in San Jose, Charles Ortloff and graduate student Shayan Mizrahosseini are trying to figure that out using this 26-foot tank.

Water is extremely precious to the Nabataeans, so ancient engineers needed to design a pipeline that would be free of leaks.

NARRATOR: Their challenge, and Ortloff's, is how to get water to flow through a pipe as quickly and efficiently as possible.

The different angles represent different choices.

NARRATOR: One choice seems obvious: make the slope of the pipe steep.

Ortloff sets the slope to six degrees and turns on the water.

Things start out well.

The water is flowing fast.

But it fills the pipe too quickly, producing an area of turbulence known as a hydraulic jump, which causes the water flow to slow down.

ORTLOFF: This is the hydraulic jump, right here.

NARRATOR: But there's a bigger problem: the pipe is now filled with water, raising the pressure.

In the ceramic pipelines, that pressure could create leaks at the joints.

ORTLOFF: So that design, where we have the steeper slope, is not good.

SHAYAN MIZRAHOSSEINI: Okay, closing all the valves.

ORTLOFF: If you can put the brick on the other side, we're just going to slide it over.

NARRATOR: Ortloff adjusts the slope of the pipe to four degrees.

A little more.

There we go.

Got it.

NARRATOR: A small change in the slope, just two degrees shallower, has a big impact on the speed of the water.

ORTLOFF: The big surprise here is that we have only changed the slope by two degrees, and yet we have a completely different flow pattern.

NARRATOR: The flow is fast.

And in this test, the pipe never completely fills with water, which would be good news for Petra's plumbers.

ORTLOFF: The entire flow has an exposed air space above the surface, and this will prevent leakage in the system.

NARRATOR: With the help of modern day tools, Ortloff has shown that the best design for delivering water fast and leak-free is a four-degree slope.

And when Ortloff measures the angle of the carved channel in Petra, he makes a remarkable discovery.

ORTLOFF: If we look at actual field measurements, we're able to see that with their pipeline, the ancient Nabataean engineers had a slope of approximately four degrees.

NARRATOR: 2,000 years ago, Petra's engineers worked out the perfect design for their long-haul pipelines.

ORTLOFF: They invented scientific principles that were only officially discovered in the West some 2,000 years later.

NARRATOR: It is clear that the Nabataeans were master hydraulic engineers.

But water is not the only scarce resource in the desert.

Wood from local trees was also in short supply.

So how could the Nabataeans build their tombs so high up in the cliff face without using large wooden scaffolding?

Paradise finds an important clue in this unusual carving, aptly called "The Unfinished Tomb."

The top is finished.

The upper area of the capitals remains somewhat crude and still in progress.

But then below that, nothing has been carved at all.

It's the natural sandstone face.

NARRATOR: To Paradise, the progression of finished at the top and barely started below can mean only one thing.

The Nabataeans started from the top and carved down.

NARRATOR: The unfinished tomb shows that Nabataeans began by sculpting the top layer of the facade, and then worked their way down the cliff face.

Getting windy again.

Yep.

NARRATOR: Back in California, Paradise tells Hunt and Rankin they must carve their facade Nabataean style: top down and without scaffolding.

HUNT: There's a lot of challenges involved in trying to figure out how the Nabataeans carved a piece like this.

I die like a Nabataean is my worst fear.

(laughing) Falling off the rock.

NARRATOR: Up to now, they've been using safety harnesses.

But the Nabataeans' top-down approach gives them an ingenious idea for how to carve without harnesses or a large wooden scaffold.

RANKIN: We've drilled into the stone here and placed a couple of pins and then put a plank on top and created a temporary and movable ledge that doesn't require a lot of material.

NARRATOR: They drive three pins into the rock and lay just a couple of planks of wood across them, forming a platform.

As their carving descends, it erases the holes they've made, leaving no sign of their platform.

By the time we get to the bottom, we've pretty much removed all evidence of any plank.

NARRATOR: The pin and plank solution works perfectly.

It could explain how the Nabataeans were able to carve so high up without scaffolding, and why no evidence for the technique can be found.

Halfway through the carving, the team makes another discovery.

RANKIN: We can move a lot of stone really quickly with these chisels.

We've been moving a surprising amount of stone every day.

NARRATOR: A little carving creates a lot of rubble.

I really cannot believe that much carving produced this much rubble.

NARRATOR: The rubble has formed a ramp.

This means they don't need their platform anymore.

Now they can just walk up to the façade.

PARADISE: When we see this much material being produced from the carving, we now realize that we create ramps from this rubble that gives you access to the facade for the stone carvers.

NARRATOR: Combining the clues found in Petra with the discoveries in the carving project, a new theory emerges for how the Nabataeans may have carved the Treasury.

They begin by climbing to the top.

Here, they cut a narrow ledge into the cliff face.

Using ancient drills, they fix pins below the ledge and lay planks across to provide a platform for the carvers.

The first thing they carve is the urn, and the upper layer of the monument.

They work their way down, sculpting the split pediment and the magnificent statues.

About halfway down, the debris from the carving forms a ramp.

Now the carvers can walk up to theacade and continue carving the elaborate capitals and the handsome columns.

We don't know of any other culture or society using this kind of engineering technique for this scale of construction.

NARRATOR: The top-down approach turns out to be a brilliant innovation for carving these tombs in Petra's sandstone cliffs.

But carving is only part of the Treasury's grandeur.

Its impressive location commands the head of the canyon and the entrance to the city.

Yet the same narrow canyon that creates this dramatic reveal can also be a death trap.

These amateur videos capture a rare but deadly desert hazard: flash floods.

Petra's average annual rainfall of just a few inches can hit all at once and pour down this gorge with lethal force.

Flash floods took the lives of 22 French tourists here in 1963, and even today could damage the Treasury.

Ueli Bellwald, a Swiss architect and archaeologist, has come to Petra to protect both tourists and the Treasury.

He's searching for clues to how the Nabataeans held back the floods.

BELLWALD: When they decided to carve this facade into the cliff, they had to do something against flash floods in wintertime.

NARRATOR: Next to the Treasury is a narrow gorge.

Here, Bellwald finds huge blocks mortared together to form an ancient dam.

BELLWALD: It's 2,000 years old and still totally preserved.

NARRATOR: But this one dam would not be enough to protect thTreasury, so Bellwald is on the hunt for more dams.

While the landscape appears to be plain rock, to Bellwald, it is packed with clues.

He notices different colors on the canyon wall.

Above this line, the stone is dark.

Below, it's lighter, which Bellwald believes is caused by mineral deposits from water once stored here in a reservoir.

Following this water line brings him to an area where two deep grooves have been carved into the canyon walls.

The grooves show where a dam once stood.

BELLWALD: All of these dams had to be anchored into the cliffs on both sides that they could easily withstand the pressure of the retained water.

NARRATOR: Following these clues, Bellwald has uncovered an ancient Nabataean dam system.

The Nabataeans built five dams.

And to make those dams even more effective, they carved a channel 140 feet long and 16 feet deep to reroute some of the water.

This created a large area to store overflow and reduce the force of the water before it reached the Treasury.

It's an engineering feat almost as impressive as the Treasury itself.

BELLWALD: They realized that if they divert the water, they allow the water to spread out to a much bigger surface.

And this reduced its speed tremendously.

It worked perfectly.

NARRATOR: So perfectly, Bellwald can't improve on this design.

Today, a team is repairing this ancient dam network so it can once again protect the Treasury.

BELLWALD: If we want to keep the Treasury for the future, we have to protect it again as 2,000 years before from flash floods.

And that's exactly what I'm doing.

NARRATOR: Because the threat of floods was so great, Bellwald believes the Nabataeans must have built the dam system and the Treasury at the same time.

In fact, scholars now believe the grand tombs, the city center, and the water systems-- most of the ancient city of Petra-- were built within 100 years around the birth of Jesus.

BELLWALD: The entire hydraulic infrastructure of Petra was built following one master plan.

NARRATOR: So just how much water did that system provide?

Back in San Jose, Charles Ortloff is figuring that out.

These are the main supplies of water from all of the cisterns, all the dams.

NARRATOR: Ortloff has mapped every water feature he and other archaeologists have discovered: eight springs for fresh drinking water, 36 dams to protect the city from flash floods, over 100 cisterns and reservoirs to collect and hold rainwater, and 125 miles of pipeline to connect many of these features into one integrated water system.

From the map and his flume experiments, Ortloff can estimate the total amount of water available to Petra's 30,000 people.

If you sum up all of the water from various sources, that would lead to eight liters per person per day.

NARRATOR: Eight liters is about two gallons.

In a world before showers and washing machines, that's more than enough water to survive on.

In fact, new discoveries reveal that the Nabataeans had enough water to transform Petra into a desert oasis.

Evidence of that water surplus is being found right next to the Great Temple, in a large open terrace.

It was named by early explorers as the Marketplace, so when Leigh-Ann Bedal began digging here in 1998, that's what she expected.

LEIGH-ANN BEDAL: Because it had been called a marketplace, I came in prepared to excavate a market.

NARRATOR: But as she began digging, at eight feet deep, she discovered waterproof cement.

BEDAL: So we knew that we had something containing water, something deep.

NARRATOR: Her team excavated further and discovered a subterranean structure.

BEDAL: We have the southwest corner here, and directly to the north is the northwest corner.

NARRATOR: Bedal located all four corners to discover overall dimeions of 140 by 80 feet, nearly the size of an Olympic swimming pool.

Then, in the middle, she found evidence of a stone platform and surrounding the sunken structure, channels, likely used for irrigating a lower terrace where soil samples suggest the area had been cultivated.

When she puzzles the evidence together, Bedal concludes the marketplace was in fact a huge ornamental pool complex including an island pavilion and a garden on a terrace below.

BEDAL: If you could imagine below us this large pool of water and then a green garden with date palm trees and flowers.

This is something that is for showing off.

NARRATOR: Throughout the city center, archaeologists are finding other decorative water features like fountains, and a canal running beside a colonnaded street.

It's really conspicuous consumption of this precious resource, water, in this desert environment.

NARRATOR: Conspicuous consumption of water in the middle of a desert?

It seems Petra resembled another flashy desert destination.

BEDAL: A great comparison is Las Vegas, where you have this very arid desert surrounding this oasis city, where everywhere you go, you see the use of water, fountains.

By diverting a precious resource into a wealthy center, it sends a message to anybody who sees it that it is a place of wealth and power.

NARRATOR: For ancient visitors, after days of traveling on camel through the hot, parched desert, entering this oasis city must have made a powerful impression.

Petra's luxurious pools and internationally inspired architecture likely sparked the legends that echoed through the ages.

Back iCalifornia, after two months of carving and nearly 2,000 years, architecture of far-off lands emerges from the rock.

PARADISE: We've got Assyrian, Egyptian, Greco-Roman, but you put it together, you stand back and it's Nabataean.

And now it's a little bit Californian.

That's right.

NARRATOR: Whether the Nabataeans were carving tombs for the dead or water channels for the living, their mastery of stone was the key to Petra's wealth and beauty.

So why did the Nabataean kingdom decline and Petra largely disappear?

Across the city, collapsed columns point to a prime suspect: ancient texts record a huge earthquake in 363.

ALCOCK: As a result, for a while, when archeologists came to Petra, any time they saw something like this, they would say, "Ah, this fell down in 363."

NARRATOR: But one catastrophic earthquake does not provide the whole picture of the city's decline.

At the Great Pl, the most luxurious place in Petra, there's evidence that hard times hit the city even earlier.

BEDAL: It may have been as early as the second century, because at that point, we find a lot of animal bones at the bottom of the pool, so it seems to have been used for trash.

NARRATOR: Found in the great pool, this layer of fallen rocks dates to around the 363 quake.

But below that, the layer of soil containing the animal bones indicates the pool filled in at least 100 years before.

And there is evidence of more destruction 100 years after the great quake, which may have fatally weakened the city's protective dams.

Large sections of Petra's main street are missing pavers.

Tom Paradise believes they were washed away in a catastrophic flash flood.

PARADISE: The floodwaters rushed down through Petra's city center, ripping up cobblestones.

This flood inundated the city and may have marked the end of Petra's golden age.

NARRATOR: Ironically, the very water that brought life to Petra may also have contributed to its demise.

Today, in the hills of Southern California, the carving team is bringing a bit of Petra back to life.

The final flourish will be a feature not found in other cultures: a Nabataean-style capital with a simple knob in its cter.

Normally, there is a detail here.

Typically, there is a leaf or a flower here.

You never really see it left in this very abstract form.

It's quite beautiful in its splicity.

NARRATOR: Paradise believes the Nabataeans choose this simple form out of respect, almost reverence, for the sandstone.

PARADISE: Their sense of the rock as a living material that had to be sort of caressed and worked was really as remarkable as their engineering expertise.

NARRATOR: And the sandstone itself becomes a tool to finish the surface of the tomb.

HUNT: I'm using the same stone that we carved off the rock.

I'm just rubbing the last little stages, just kind of carefully finishing off that last surface.

NARRATOR: Stone is at the core of Nabataean lives.

The very name for their city, Petra, comes from the Greek word for rock.

PARADISE: The Nabataean relationship with their sandstone was fundamental to who they were.

They're born in this valley of rock, they live in this valley of rock, and then when they die, they are buried in the rock itself.

These hewn tomb facades become their final resting place.

NARRATOR: Each year, over half a million tourists retrace the steps of the explorer Johann Ludwig Burckhardt and gaze up in awe at the Treasury.

But in the two centuries since Petra was re-opened to the Western world, its distinctive engineering and culture is proving equal to that of any ancient civilization.

TUTTLE: Petra is more than a city.

It was the seat of a kingdom, a kingdom whose peace and prosperity was the envy of the ancient world.

NARRATOR: Cisterns, channels, dams, even fountains and pools.

The Nabataean mastery of water fueled their astonishing city of stone.

ALCOCK: The water features are underpinning everything.

If the Nabataeans couldn't control the water, you wouldn't have a city here.

NARRATOR: Over 2,000 years ago, a desert tribe settled among these forbidding cliffs and transformed this hostile landscape into an oasis.

PARADISE: The Nabataeans learned how to maximize these limited resources to produce a society and a culture that thrived and prospered for hundreds and hundreds of years.

NARRATOR: Burckhardt came here chasing legends of a city lost in the sands of the desert.

A city with riches from all over the known world, buildings that rivaled Egypt and Rome, and fountains and pools overflowing with water.

Today, it's clear many of the legendary splendors of the lost city of Petra are true.

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