♪♪ -Towering above the modern city of Granada in southern Spain stands one of the most magnificent palaces of the medieval world, the Alhambra or Red Fort.

Built over 250 years by a mighty dynasty, it's an extraordinary complex of fortresses, exotic palaces, gardens, and fountains from a time when Spain was under Islamic rule.

Today, it represents the pinnacle of Islamic art, a dazzling array of intricate ceilings and geometric patterns attracting visitors from all corners of the globe.

♪♪ But behind the splendor is a hidden story.

An army of archaeologists, specialists, and historians are working to restore the palace.

Despite decades of work, the Alhambra is still shrouded in mystery.

How were such intricate patterns produced on such an unimaginable scale?

What do the thousands of inscriptions on its walls reveal?

♪♪ How did this Muslim dynasty flourish here in Spain for so long?

And above all, how did they build on a rugged hilltop, the most stunning medieval fortifications of the ancient world?

♪♪ [ Birds chirping ] From the outside, the vast, palatial city of the Alhambra looks like an austere fortress, but inside is a treasure trove constructed between the 13th and 15th centuries by a great dynasty of Muslim kings called the Nasrid sultans.

And to understand what makes it so special, you have to look at the different parts of the complex separately.

Jesús Bermúdez lived at the Alhambra all his childhood with his father, the museum's director.

He's now an archaeologist specializing in Islamic art.

-The Alhambra is a city that was conceived at the end of the Islamic era in the West, developed over a period of 260 years.

♪♪ -There were 24 Nasrid sultans, some building or refurbishing the palaces and expanding the city and its fortifications.

♪♪ -The city was also conquered by Christian troops, who decided not only to keep it, but also to use it, to exploit it, to live in it.

This also implies new changes, new transformations.

-So the Alhambra is actually a tangle of different buildings and eras.

Jesús wants to clarify the chronology of this mixture.

So he's teamed up with Hubert Naudeix, a specialist in archaeological modeling, to make a virtual model of the different parts of the settlement.

-The Alhambra is built around three main zones.

The military zone located on the highest part of the mountain known as the Alcazaba... ...the residential Medina for crafts and products destined for the court, and a zone where the palaces stand, an area exclusively reserved for the residents of power.

-There are three main palaces built from the 14th century onwards.

The Ismail Palace was built first, then the Comares Palace, and finally the last section, the Palace of the Lions.

-Which means that the different palaces are placed in chronological order.

So we're expanding more and more.

-Exactly.

But to fully understand how all these developments came about, I think we need to start with the Alcazaba.

♪♪ -The Alcazaba means "citadel" in Arabic.

Built in the early 13th century at the very edge of the hilltop, it was the first part of the Alhambra to be built.

It's clearly a defensive site, but what led Arabs to build a fort here in southern Spain?

[ Horses neighing ] In the year 711, six centuries earlier, Muslim troops from Arabia and North Africa invaded the Iberian Peninsula.

They conquered most of what is today Spain and Portugal, creating a new territory known as Al-Andalus, which lasted 300 years.

But civil wars meant the region broke up into smaller dynasties, and Catholic kingdoms from the north conquered these territories, pushing back to the south.

But one part of southern Spain escaped -- the Sultanate of Granada -- and in 1238, the founder of the Nasrid dynasty, Muhammad I, made Granada the capital of his kingdom, building on a hill overlooking the city, a defensive fortress, the Alcazaba.

Strangely, despite its strategic position, the building had been largely ignored by historians until now.

Architect and historian Adelaida Martín Martín is trying to understand the key to its strategic success.

-[ Speaking Spanish ] -Most books always focus on the palaces.

Knowledge of the Alcazaba are essential to understanding the origin and history of the Alhambra.

-Protected by a double row of walls, the houses were sheltered inside, and keeping watch above was a set of towers.

♪♪ -Some of its towers are truly independent fortresses, totally foreign to Andalusian military architecture.

However, it's the dungeon that attracts the most attention.

-To understand why the dungeon was particularly important, Adelaida decides to explore the design and function of each of its six levels.

♪♪ With their simple vaulted ceilings and thick walls pierced by small openings for adjusting fire, the first two floors are clearly intended for soldiers.

But from the fourth floor onwards, she notices something different.

♪♪ -The great variety of vaults shows that this room had great importance.

We find, for example, a drop vault supported by groin vaults.

♪♪ -Such grand features are an unexpected design for a military tower.

Could the room have had a special function?

Adelaida then finds a 14th century text by the most famous writer and historian of Granada, which describes the daily life of Muhammad I.

♪♪ -According to the texts of Ibn al-Khatib, Muhammad I, after holding his audiences, would then go up to his quarters to rest.

This brings us to the fifth level of the tower.

The rooms were arranged around a central courtyard.

So this is a dwelling, probably the one used by Muhammad I, the first known dwelling in a tower of Andalusian architecture.

♪♪ -Complete with its lookout on the roof, by combining the administrative and residential functions into one highly defended building, this was the perfect place for Muhammad I to run the entire fortress and govern his new kingdom.

And clearly he succeeded.

Through skillful alliances and diplomacy, the Kingdom of Granada flourished for 200 years, paving the way for an idyllic oasis to expand across the hilltop.

The Alhambra had been born.

♪♪ After Muhammad I's death, a succession of sultans followed until, 60 years later, a certain Yusuf I took to the throne.

His reign saw the start of great riches and success for what had become known as the Nasrid dynasty.

The territory was surrounded by Christian kingdoms, and so Granada became a haven for thousands of Muslims, among them architects, craftsmen, and artists who were soon pooling their talents to adorn the Sultan's seat of power, starting with his new home, the Comares Palace, one of the most spectacular examples of Nasrid architecture in the entire Alhambra.

♪♪ The palace is centered around a vast courtyard and pool and dominated at one end by the most massive of all the Alhambra Towers.

Inside, it's breathtaking.

The vast hall is a perfect cube, decorated with magnificent patterns and calligraphy, and its crowning glory above is an immense dome of stars.

The big question is, how is it constructed, and what does its hidden symbolism mean?

♪♪ -[ Speaking Spanish ] -The 13-panel self-supporting structure is exceptional in its size.

Its a framework measuring 13 meters on each side and seven meters high.

Its dimensions are therefore impressive.

-But it's not just the scale that's remarkable.

-Structurally, it's composed of pine and poplar pieces.

According to current documentation, there are over 8,000 pieces.

-Each one was painstakingly painted, and an idea of the original effect can be seen in this colorful reconstruction from the 1960s.

Correa's recent studies reveal another secret hidden in the structure itself.

-[ Speaking Spanish ] -When we studied it, we found that the opening delimited by the walls of the tower is bigger than the bottom of the dome's framework.

There's one element that bridges the gap between the room and the framework, and that's the frieze.

This creates an effect as if the framework were floating.

It's a technical solution that meets a symbolic need, a ceiling that evokes the sky.

♪♪ -The Nasrid craftsmen want it to represent a deeper meaning -- the different heavens mentioned in the Muslim Koran.

♪♪ -The seven heavens are formed by rows of 8-pointed and 16-pointed stars, and the eighth heaven is the throne of God.

And in the center, the chair that crowns the eighth heaven.

-This reference from the Koran was a huge statement to give the hall prestige because it had a crucial role.

-In the hall of Comares was the Sultan's throne, which was meant to be compared to the way God ruled.

It's a way of legitimizing the power of the Sultan.

♪♪ -It's not just the vaulted ceiling that makes the throne room so iconic, it's the geometric patterns.

♪♪ -[ Speaking Spanish ] -One of the most distinctive features of Islamic art is the use of geometry.

It can be found in all manifestations of this culture, in all buildings, in all materials, in decoration, everywhere.

The Alhambra is a perfect example.

♪♪ -Nasrid craftsmen pushed the use of geometry to the very limit, turning it into an art form to create a myriad of mosaics.

They are so complex and intricate that, for centuries, people were puzzled as to how they were made.

♪♪ -Living in Granada, I was particularly interested in this whole lesson in geometry transformed into art at the Alhambra.

So I started to look at it intuitively.

-Artist and university art professor Manuel Vela has been unraveling how the mosaics were designed.

-Well, what I've been trying to do is find the traces that lie hidden beneath what we see today.

Underneath lies a skeleton, an armature that supports it.

-In other words, he needs to find the tracings underneath used to draw out the geometrical patterns.

One of the most interesting is called the pinwheel.

-The motif of this design is very simple, but difficult to see at first glance.

From the grid, by outlining certain squares, we can draw circles, and on these circles we can also draw other inscribed squares so that we obtain an eight-pointed star.

Eight-pointed stars aligned diagonally.

It's the basic motif, and one of the most repeated in the Alhambra.

Starting from this motif, you highlight one series of lines and forget about the others.

-The Nasrid artists left no documents describing how they drew their motifs, except for a few rare exceptions.

♪♪ -[ Speaking Spanish ] -In this corridor, we find one of the few medieval documents that explains how the design we see on the wall was created.

The lines that make up the grid are clearly visible.

We can also see the circle drawn with a compass, then the tangent line to the circle.

By applying the same process as before, marking certain lines, the drawing appears.

♪♪ -For some mosaics, the amount of underlying tracing was dizzying.

It was a world where the laws of geometry were used to create genuine works of art, and a way for believers to contemplate the infinite nature of God in a religion where literal representations were forbidden.

Above all, the Nasrids' deep knowledge of science and geometry reveals something which is often forgotten.

That it was the Arabs who first translated Greek mathematics and introduced it to medieval Europe.

♪♪ Just when the Alhambra was flourishing so well under Yusuf I, there was an abrupt change when he was assassinated.

The throne was left to his 16-year-old son, Muhammad V, who was then forced into exile to Morocco.

There he discovered a whole new set of inspirations -- palaces, mosques, fountains.

♪♪ When he regained power in 1362, he brought it all back to make his own mark on the Alhambra.

A new palace was born.

The Palace of the Lions.

♪♪ This was something in a whole new style, with galleries and arched cloisters supported by over 100 columns.

It's a forest of white marble.

And in the center, 12 water-spitting lions which give the palace its name.

But it's one particular feature that makes the palace unique.

The muqarnas.

The huge honeycombed vaults which resemble giant beehives.

They're everywhere.

Like a three-dimensional jigsaw puzzle, muqarnas are made up of hundreds of small interlocking blocks, but leads to an almost impossible conundrum.

How many blocks are used and what shapes are they?

To try and crack the code, Ignacio Ferrer is using 3-D computer models.

Problem is, the only original information he has is two centuries out of date.

-[ Speaking Spanish ] -When I try to apply these rules and reproduce the muqarnas of the Alhambra, it's not possible because these plans only represent two-dimensional figures into which we can insert parts.

But these flat figures can actually correspond to seven or eight 3-D variations.

In this case, up to nine variations are possible, including a version that is, for example, completely convex, or the opposite version that is completely concave.

♪♪ -To fill the gaps in his knowledge, Ignacio went back into the field to figure out the basic shapes needed to assemble various different muqarnas.

Turns out it was much more complicated than he thought.

-If we only used the few pieces seen in these manuscripts, we'd never be able to create the richness of the Alhambra.

In the Alhambra, there are many more figures that give rise to many more pieces.

I've discovered 15 figures that give rise to more than 21 variants, and from these variants, we obtain 40 or more pieces.

As research progresses, it will be possible to list the full wealth of the Alhambra muqarnas family.

♪♪ -At the very heart of the Palace of Lions is one of the most commonly used features of the Alhambra courtyards, a majestic fountain.

♪♪ The fountain of the 12 lions symbolizes power and the four rivers of Paradise described in the Koran.

Of course, without water, the Alhambra would have never been possible in the first place.

Which leads to an intriguing question -- how did the Nasrid engineers manage to harness the water and bring it to the top of the hill?

♪♪ In the hills above the Alhambra, Luis García Pulido has been searching for archaeological remains to figure out how they did it.

-[ Speaking Spanish ] -This is the first part of an aqueduct that would have crossed this ravine.

You can even see the marks of the planks here.

They were about 18 or 19 centimeters high.

The planks that served as a framework for the construction of this mass.

And there's also a series of rows of bricks and what appears to be a stone base.

And over here you can see the canal.

With the two side blocks that form the water conduit.

-Bit by bit, Luis maps the stages in the construction of the water system, which turns out to be a remarkable network of canals, aqueducts, and water channels.

The successive grooves of the canals, or acequias, are still clearly visible on the hillside to the east of the Alhambra.

-This is where we are.

We are here in one of the first sections of the Royal Canal.

There are several routes for this water channel.

And then there's a series of structures higher up linked to the later routes the canal took.

It's a fairly long pipeline, because to reach the Darro River, where it emerges at a higher level than the Alhambra, you have to travel at least six kilometers.

♪♪ -Before entering the Alhambra, the network divides into two branches, irrigating the gardens of a small pleasure palace.

In the 14th century, the network became even more sophisticated with the addition of an animal-powered system for raising water.

♪♪ -The water was raised by a paddle wheel.

It rose nearly 60 meters and then another 60 meters.

A total of 120 meters to this hilltop basin.

-From here, it was channeled not just into the Alhambra itself, but also into the royal farms, which produced food nearby.

This remarkable network of water channels was the only water source for the Alhambra for 700 years, and is still essential today.

For the sultans, water was just as precious for gardens as it was for daily life.

Designed to entice the senses, they combine scents, aromas, and colors with the sound of water.

A perfect example still exists to this day.

in the royal estate of the sultans overlooking the Alhambra called the Generalife.

The water enters the palace behind a stairway whose banisters cleverly serve as gutters.

And then, within a series of courtyards, they feed a mosaic of magnificent gardens.

♪♪ Pools and fountains surrounded by neatly clipped hedges, flowers, and fruit and vegetables.

♪♪ The Nasrid gardeners used a clever technique, lowering their flower beds below the surrounding ground to create a carpet of flowers level with the pathways.

Gardens were so significant they were frequently the subject of Arabic poetry.

♪♪ ♪♪ -[ Speaking Arabic ] -"I am the garden adorned by harmony."

-[ Speaking Arabic ] -"Contemplate my beauty and you will understand my rank."

♪♪ -Poetry and writing are a huge tradition in Islamic decoration, but the Alhambra takes it to extremes.

Over 10,000 inscriptions cover every square inch.

♪♪ -[ Speaking Arabic ] -"The crystal sky shows wonders there."

-[ Speaking Arabic ] -"Written, they fill the pages with beauty."

-[ Speaking Arabic ] -"Light is one, and the colors multiply."

-[ Speaking Arabic ] -"Opposite or the same as you wish."

-[ Speaking Spanish ] This is one of my favorite Alhambra poems.

It refers to that precious glass ceiling, the only one left in the Alhambra.

The poem is also very interesting because it says that here was the throne of Muhammad V.

♪♪ -But how and why did writing become such an important decorative feature here?

José Miguel has translated all the inscriptions, among them one of the most spectacular in a tower so fragile it cannot be shown to visitors.

♪♪ -[ Speaking Spanish ] -This is one of the few poems in which the word "Alhambra" appears in writing.

From here to there.

It's in this area here that the word "Alhambra" appears.

-José Miguel and his photographer are capturing some of the best examples.

-Very good.

You've got a good resolution.

You can even crop it, enlarge it.

It's perfect.

Look here, the calligraphy starts at the top.

If they normally sat on the floor and leaned on the wall, they never leaned on the word because the word is sacred and honored.

-This one small palace epitomizes the special talent of Nasrid calligraphers.

-Here we have a magnificent summary of the Alhambra's calligraphic styles and content.

We have cursive calligraphy, more curvilinear.

This is Kufic calligraphy, very solemn and geometric.

And at the Alhambra, there's also a new type of calligraphy not known in the East.

Architectural Kufic calligraphy.

The letters form small arcs as if supporting the entire composition, which develops all the way to the top.

-It's an exceptional creativity used to illuminate the Nasrid dynasty's motto.

-[ Speaks Arabic, then Spanish ] -"God alone is victorious."

It's one of the most important inscriptions in the Alhambra, forming a genre in its own right.

It appears on all the buildings of the Nasrid dynasty.

-It's a playful use of words where the content shapes the design of the room.

-We have four poems of eight verses carved into the four corners of the room.

They begin in this section.

They continue along the wall.

They make a corner as if it were an open book.

They go down to the bottom of the verses and continue down to the end.

It's clear that the poets were involved and designed the building, the decoration as a kind of three-dimensional book.

♪♪ -Writing and geometry were so widely used because representations of people and animals were usually forbidden.

But here there's a spectacular exception.

A few meters from the decor, typical of Islamic architecture, there are three vaults decorated with images of people, a vivid portrayal of the Nasrid world.

Given such strict rules, what are they doing here in an Arabic palace, and what do they show?

-[ Speaking Spanish ] -The central scene depicts the kings of the Nasrid dynasty.

The side vaults depict hunting, combat, and court scenes.

They look like a series of unrelated images, but when you read them, you see that they tell a story.

-A story where Muslim warriors fight Christian knights for the hand of a damsel and emerge victorious.

♪♪ -The motifs depicted are common in medieval painting of this period.

It could have been a Christian mind, but we can see that there's a great deal of overlap between the two cultures.

Motifs are shared.

We can't rule out that the hand that executed it was Muslim.

-This is what makes the Alhambra so unique.

A rare example where figures are permitted outside a religious setting, and what it shows is how the adjacent cultures and styles influenced each other in a kingdom whose survival depended on good relations with its neighbors by negotiating treaties, alliances, and trade networks.

♪♪ The Nasrid kingdom was perfectly situated for Mediterranean trade.

They exported dried fruit and sugar cane, grown on the fertile plains watered by the Sierra Nevada mountains.

But there was one particular merchandise that built the reputation of the Nasrid kingdom above all others -- ceramics.

With a metallic sheen and shimmering blue and gold, they became highly sought after across Europe and beyond.

♪♪ Archaeologist and historian Alberto Porras and his team are trying to work out where and how these priceless ceramics were made.

So he is studying the ruins in an area of the Alhambra called the Medina, the larger zone behind the palaces were the craftsmen lived.

Problem is, there's very little left.

-[ Speaking Spanish ] -We knew that pottery was produced within the walls of the Alhambra.

We found a series of structures, but they weren't very well studied.

It's only now that we're reinterpreting them, analyzing the whole space, and reinterpreting the whole Medina area, and specifically these quarters, quarters that were largely occupied by craftsmen.

-Alberto has found some ruins buried in the vegetation.

Some kind of furnace or kiln.

Could these have been used to make the Alhambra's priceless pottery?

-The curious thing about this kiln is that, unlike the others which have been restored and modified, this one has remained intact.

What we're interested in, therefore, is analyzing the kiln walls to see if we have any evidence of the type of production that took place here.

-Here?

-Yes.

-The experts are testing for specific chemicals on the surface of the walls.

[ Beep ] -At first glance, you can see that there's iron, copper, manganese, and zinc.

-There's cobalt.

I'm interested in the cobalt blue of ceramics.

-This level of cobalt is highly significant.

It doesn't appear in the other furnaces.

-What this might show is that this kiln was used for the production of blue and white pieces, typical of the Nasrids, made with cobalt oxide.

♪♪ -These chemical signatures reveal ceramic production and trade on a vast scale they never imagined.

-We've located 12 or 15 kilns, but the number may be even higher, as many others appear hidden in the ground, covered by vegetation or by buildings built on top of them that prevent them from being seen.

In other words, we're dealing with a potter's quarter of remarkable size.

♪♪ -The pieces in the Alhambra Museum show a remarkable finesse, whether used for sultans' dining tables or as decoration.

Known as Alhambra vases, highly prized by the courts of Europe, only a handful remain today.

♪♪ And the most prestigious is this, the Gazelle Vase, with its intricate blue and gold decoration.

It marks the very pinnacle of the Nasrid potters' achievements.

♪♪ ♪♪ By the 15th century, the Alhambra was a radiant and prosperous city, a monumental, complex unique in scale and architectural finesse.

Numerous grand residences, always organized around a central courtyard, housed the nobles and officials.

Its Medina, served by two main streets, was as equipped as any Muslim city, with a mosque, baths, and shops, and a vast district of craftsmen dedicated to the needs of the palace.

But change was in the air.

[ Horses neighing, swords clashing ] In 1453, Muslim Ottoman troops seized Christianity's great capital city, Constantinople, which today is Istanbul in Turkey.

It put an end to the Christian Empire of Byzantium, which had ruled for over 1,000 years.

Europe was in shock, but there was no question of peace with the Muslim kingdom of Granada.

Christian kingdoms rallied against the Nasrids, and within 40 years, it was under siege.

The Nasrid forces were no match for Catholic artillery.

The last sultan of the Alhambra, Boabdil, was forced to surrender.

The Kingdom of Granada was no more.

♪♪ When the Catholic kings finally discovered the Alhambra from the inside, they were dazzled.

This was no rebellious city.

It was a spectacle of extreme refinement in architecture and decoration, expressing eight centuries of Islamic culture.

Rather than dismantling it, they became its protector and paid for all the damage to be repaired.

♪♪ Conquered, the Alhambra was saved by its magnificence.

But just as calm was returning, there came its most drastic, chaotic period of change.

♪♪ In 1525, a royal wedding had an unexpected impact.

Charles V visited the palatial city during his honeymoon with Isabella of Portugal.

He was instantly captivated and decided he wanted a palace of his own there, so he knocked down a few buildings and built an immense rectangular edifice right next to the Nasrid palaces.

The contrast could not be greater.

From the outside, the palace is an almost perfect square, with a vast circular courtyard set within it.

♪♪ This was the statement on a grand scale, a way for the Christian monarch to rival the Nasrids while clearly following in their architectural footsteps.

♪♪ Other buildings, such as the church built in the 16th century on the site of the original mosque, continued to Christianize the site.

Meanwhile, Muslims kept a low profile and had to convert to Christianity to remain in the country.

♪♪ Those whose ancestors had built this great kingdom were finally expelled by the end of the century.

But worse was to come.

[ Horse neighing ] Two centuries later, there was a lethal blow.

The Napoleonic War swept across Europe.

In 1812, having used the palaces as barracks, Napoleon's armies dynamited its fortifications and plundered its treasures.

♪♪ A violent earthquake further ruined the buildings and the Alhambra and all its former glory was left to decay until there was an intriguing twist of fate.

In 1828, a certain American writer and historian called Washington Irving arrived in Granada.

♪♪ -[ Speaking Spanish ] -Washington Irving toured this monument with the impression that the Alhambra was going to fall apart in no time, and this is the impression he gives in his book, "Tales from the Alhambra," published in 1831.

-Juan Manuel Barrios is an art historian studying the Alhambra in the 19th century.

-He and other painters and artists who came from England, France, and Germany to visit the monument made the Alhambra famous the world over.

His "Tales of the Alhambra" became the guidebook that all travelers took with them.

-Washington's work became so influential that it provoked a change of heart in Spain.

-The book changed the trajectory of the Alhambra deterioration and attracted the attention of the Spanish authorities, who began to donate money for its restoration.

♪♪ -A vast project began to restore the Alhambra in 1836.

The problem was, without knowledge of Muslim architecture, no one in Europe had the slightest idea how, which led to some monumental mistakes.

The most spectacular example is in the Courtyard of the Lions, the small kiosks topped with a dome in the 19th century.

-The Alhambra never had shiny ceramic domes, but some architects thought that it should have domes like in The tales of the "Thousand and One Nights."

-Finally, the Alhambra managed to escape these exaggerated errors when an architect called Leopold Torres Balbás took over the restorations in 1923.

-He was a great historian of the monument, which enabled him to make excellent decisions.

In the Courtyard of the Lions, Leopold Torres Balbás was confronted with the famous dome and decided to remove it.

He developed a series of hypotheses on the ideal reconstruction and came to the conclusion that the best one is the one we see here.

♪♪ -Most of these excesses have now been corrected, but there's still one intriguing spot where the flamboyant restoration work of the 19th century can still be seen.

The Royal Baths at Comares.

♪♪ -[ Speaking Spanish ] -It's one of the most important buildings in the Alhambra because it's probably the only building from the medieval period with bathing facilities that has been preserved in Islamic architecture in the West.

That's why, for us, its conservation is so important.

These were the private baths of the kings, of the court, not public baths.

When the Sultan used the baths, he'd enter from upstairs, stripped naked in the vestibule, then go naked to the lower part, to the resting room.

Then he'd move on to the hot zone where the steam baths were served.

Finally, he returned to the bedchamber to rest.

-This magnificent area was extensively restored in the 19th century, but although the original structure and motifs have been respected, in some places, the restorers used the wrong colors.

-In this room, for example, it can be seen that the back wall retains some of its original color, while the other wall has been repainted in the second half of the 19th century, and critics of 20th century scientific restoration have compared the visual effect of the colors in this room with a bullfighter's costume.

♪♪ ♪♪ -Today, there's no question of inventing or reinterpreting the missing pieces.

Thanks to an army of specialists, the Alhambra is now as close as it can possibly be to its dazzling past.

But it's fragile, and every carving and inscription needs constant care.

So, the big question is, how will they do it long into the future?

One answer lies here in the plaster workshop, where fragments of all ages are painstakingly restored, from fine plaster casts and carved reproductions to restoring damaged fragments of an original piece.

It's a huge operation for which the head of the workshop, Ramon Rubio, has developed a highly specialized kind of mortar.

♪♪ -[ Speaking Spanish ] -Whenever there was a deterioration, an element that fell due to the seismic movements that occur in Granada, the piece would disappear and we'd just rebuild it with plaster.

But today we've invented and patented a new mortar.

And the advantage of this mortar is that it is totally invisible to normal natural light.

To detect it, you have to irradiate it with ultraviolet light.

♪♪ Anyone in real time, now or in the very distant future, will be able to tell the difference between the restored part and the original.

Because this mortar can be reinstated, varnished, painted, and still retains its power to fluoresce.

We have used it in murals such as the famous leather paintings in the King's Room.

-In its journey across the centuries, the Alhambra will now leave a luminescent trace, which historians and archaeologists of the future can follow to shed light on its remarkable history.

It's a story of a culture which, faced with extinction, firmly made its mark by pushing art to its limits to give the West its very own share of the East.

♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ♪♪