Ancient Megastructures: Alhambra

Nestling in the Andalusian mountains of southern Spain sits a magnificent fortress, the Alhambra. Its brooding citadel dominates the Granada skyline. Its great walls have 37 gigantic towers, and it took over 150 years to build. But the Alhambra is more than just a military stronghold. It's a pleasure palace of exquisite courtyards, a blood-soaked theatre of deadly intrigue, and the most famous surviving monument to Muslim engineering in the Western world. Granada, southern Spain. In the 13th century, this ancient city lived under Muslim rule. It stood at the point where the great Granada plain rose to join the mountains of the Sierra Nevada. Guarding over that junction is the magnificent fortress known as the Alhambra. It was intended from the outside to make a military statement, to show that the rulers were powerful. But it's not just a fortress. It's a spectacular network of palaces, each one different, built by a succession of sultans across 150 years. Each new ruler has to build a new palace, because if you're a ruler, you have to build. These palaces are surrounded by an exquisite suite of gardens, cooled by pools and fountains fed by fresh mountain water, all watched over by a brooding fortress designed to intimidate. Yet for all its beautiful bravado, the Alhambra is not a triumphalist monument. It was born of fear. 1238 AD. The Muslim world had been under attack from Christian crusaders for over a century. The 500-year-old Muslim empire in Spain was shrinking under pressure from the rising Christian kingdoms in the north. The general trend was for Christian powers to push southwards, and the early 13th century is most definitely a period of dire crisis for Muslim power. Dr Amira Bennison describes this turning point in the history of Muslim Spain. They faced pressure from Castile and then Aragon in the eastern part of what became Spain. The empire collapsed, and it was in the period of collapse that we see local lords, like Muhammad I of the Nasrid dynasty, beginning to carve out a niche for themselves. Not much is known about Muhammad ibn Nasir before he enters Granada. He was just one of the many minor sultans warring over the scraps of the fading Muslim empire. When Castile advanced on his northern territories, he headed south and took over Granada under circumstances that are shrouded in mystery. He's an opportunist, if you like. An enterprising individual who's making best use of the political circumstances of the time to try and secure the allegiance of various cities, including Granada. Once there, Muhammad climbed the wooded slopes above Granada in search of a location to build a fortress in which he could safeguard his family, the Nasrids, from the Christian advance. He heard of a fort built a hundred years earlier by a previous dynasty and climbed the hill to investigate. Before him, the ancient Arab castle sat on the Sabica Hill, framed by the mountains of the Sierra Nevada. It was the perfect site for a fortress. In his mind's eye, he could see it grow before him. Muhammad had found his ideal location. The Sabica Hill is a good place for a fortress because it's a hill nearly 100 meters high. Don Antonio Orejuela is an expert in the architecture of the Alhambra. He believes the geography of the area is perfect for a stronghold. In the back are the last hills of Sierra Nevada, so no army could enter the hill from behind. Muhammad instantly recognised the site's defensive possibilities. He started to outline the citadel of his dreams. The first step was to rebuild the existing fortress, known as the Alcazabar, into a stronghold large enough to support his troops. This would guard a suite of palaces surrounded by luxurious gardens that would form a royal quarter on the northern side of the hill. And beside it, a township called a medina, housing the hundreds of people needed to run this royal bastion. Encircling it would be a gigantic perimeter wall dotted with guard towers to fight off marauding attackers. But first, he needed to build a watchtower. Defensive towers would form an integral part of Muhammad's concept for the Alhambra. The basic building block of each tower was a square chamber, repeated at every level. These chambers would be filled with vaulted arches that let light flood through the interior spaces. The first tower Muhammad would build was the Torre de la Vela, known as the Watchtower by the locals. This brooding giant was bigger than anything Granada had seen before. It sent a message to both Muslim and Christian alike. It was a statement to the people of Granada. Nasrid rulers were trying to say, We can defend you, but remember that we are your rulers, and that we are powerful, and that we dominate you as our subjects. So this watchtower needed to be strong enough to hold off any attackers while builders constructed the rest of the Alhambra. For this to work, Muhammad wanted it positioned on the extreme western tip of the Sabiqa hill, where it would act as the anchor for his planned new fortress. Here it would be surrounded by steep slopes on three sides, protecting it from attack as it dominated the Granada plain. Constructing a huge tower on a precipice using nothing but primitive tools would not be easy for the builders. But the solution to their problem lay right beneath their feet. They were building their fortress on an almost sheer drop, great for defence, and a gigantic gash in that steep slope reveals the amazing substance that made the Alhambra possible. Beneath the Torre de la Vela, civil engineer Ed McCann investigates the seam of this red rock. One of the secrets to the construction of this place over here is this material here. This is the famous Alhambra conglomerate, a mixture of clay and sand and stone. So if you get a handful of it, get it nice and wet, what happens is that the clay starts getting sticky, so this material becomes mouldable, and they use this stuff to make that. It gave the builders a ready-made source of materials on site. This sped up the construction timetable and kept them close to the fortress they were building. Its colour also gave the stronghold its name, the Madinat Alhambra, which means Red City. This amazing early cement allowed the builders to lay a strong concrete base for the Great Watchtower, without having to quarry and transport huge amounts of stone. But there was a serious flaw in the building's design. The core of the tower was supported by tiers of arches. The full weight of the building resting upon them. Halfway through construction, the builders realised that the arches were not strong enough to take the load. Muhammad's first tower could collapse in on itself at any minute. As an extra means of support, they filled in part of the basement to provide a solid foundation for the tower to rest on. But their hasty repairs failed to fix the problem. Muhammad's fortress was in danger of falling down. The Alhambra's main watchtower, the Torre de la Vela, was in trouble. As its builders began to erect its upper levels, it was clear that the lower levels were not strong enough to support them. Ed McCann explores to find out why. Now this area is meant to be an awful lot more open than it actually is. What we've got here are a series of arches that have been completely bricked up. This one here, for example, should have been as open as this one over here. You don't do this for nothing. You do this when the structure isn't working properly and when we look around we can see lots of evidence around here of a structure that is in distress. Yeah, there we see it. What we've got over here is a very substantial structural crack running right from up the top there all the way down the wall, right the way to the floor. And it's a crack literally that you can put your hand inside. What this shows us is that this wall here, this one here, has been pushed bodily away from this one here, allowing this crack to form. The question is what pushed this wall over? The weight of the tower was crushing the arches that were holding it up, pushing it out of shape and cracking its walls. So what they've done when they've seen the cracks appearing is they've bricked up the area under the arch and turned it into a wall so that all of the forces come down in a straight line. Muhammad's builders bricked up the arches to provide the crucial support needed, but the interior of the tower no longer bore any resemblance to its original design. The Sultan's vision of arched spaces with a varied interplay of light and shadow has vanished entirely. In its place is a brutal monument to the needs of the age. Those needs were defensive. Muhammad's great watchtower looks out over the plains of the Sierra Nevada with the distant hills of the kingdom on the horizon. Covered by a modern city today, the watchtower once looked out over open farmland. Here it's ideally sited to form the heart of a great intelligence network that guards Muhammad's kingdom. And the Sultan has need of such a network. By 1245, just seven years after he took over Granada, Muhammad has already lost his northern territories to the Christian advance and his army is too small to win them back. This is not a man who is surviving on the basis of military might because those days are long gone. He's surviving on information and on his relationships. As Professor D.D. Fairchild-Ruggles knows, the Alhambra's continued existence is dependent on good intelligence. So he needs information. He needs to know when enemies are approaching and he needs to know what's going on. To gather this information, he installs a network of signal towers designed to warn him of the Christian advance. This network of fortlets was known as taliyahs. They were part of a vast information gathering system that garnered intelligence from people who passed through the area, providing early warning of Christian troop movements. Signals warning of impending attack would be transmitted from the top of the tower by means of special mirrored plates, smoke or fire. From there, they race from tower to tower, travelling into the kingdom towards the Alhambra. Until ultimately, they arrive on the roof of the Alhambra's watchtower, where they warn the sultan of impending attack. In 1246, messages from his signal towers tell Muhammad that the Christian king, Fernando of Castile, has taken Hain, 66 kilometres north of Granada. It's a major blow. Muhammad realises that he cannot stop the Castilian advance. He needs more time to complete his fortress. He strikes a deal with Fernando in return for guarantees of his own autonomy. Muhammad not only gives up Hain, he helps Fernando seize Seville. It's a clever move, but it's also an admission of weakness. A lot of people were shocked that he had, in effect, abandoned Hain. The reason he did that was to protect the city of Granada. He felt that this was a cost that had to be paid to protect the enclave he'd created. Muhammad knows the uneasy truce might break down at any moment. He wants to ensure that his citadel is secure as quickly as possible. To do that, he must finish the Alcazabar fortress, which will house the troops guarding the Alhambra. The plan is to build a triangular castle anchored upon three towers. From here, a gatehouse in the back wall provides access to the rest of the Alhambra. Working with the naturally-occurring Alhambra conglomerate, the builders use moulds to erect its three-metre-thick walls. The key thing about the conglomerate is the ease with which you can build, and this wall here shows exactly how they did it. Basically, what you do is you build yourself a mould. You have two big panels joined together by a series of timber poles, and you can see where the poles would have gone here. Put the poles through, then put your timber panels in, tie them together, and then you throw in your conglomerate, a bit of water, and you ram away, pounding it down, forcing the particles of the conglomerate together in a really tight concrete-like mix. They leave the layer to dry, then climb up onto it and repeat the process. But the engineers know that there's a significant downside to this method of construction. With water and wind, this stuff gets blown away, and what you're looking at here is an eroded surface that, over many years, has lost its strength. And to prevent that happening, what they did was they applied a lime and sand stucco, which is what this finishes here. So it's just basically sand mixed up with lime and a bit of water and applied like a plaster, and that's much, much better against water. And then the job would be done. In this way, the walls and buildings that made up the Alcazabar could be erected swiftly and efficiently under the defensive shadow of the Torre de la Vela. Looking down from this watchtower, the ground plan of the buildings that once filled the Alcazabar is still visible. This thriving miniature township houses the troops that guard the Sultan and the people who look after them. The central street in the heart of the Alcazabar has five warehouses and 13 private houses. A tannery, kilns, storehouses and a bakery supply the population's needs. The Alcazabar is teeming with life. And rising above them all are the great defensive towers that overlook the fortress. Sultan Muhammad must have wandered through his stronghold and felt that his dynasty could finally be secure. But there was more to the Alhambra than just a fortress. Because beyond the Alcazabar, he plans a suite of palaces that will eventually house the Sultan and his family, along with gardens and a mini-township to support them. The Alhambra had a population of not only the Sultan and his family, but of course his followers and servants and guards. It was a very large population that lived in that palace. So one can think of it as a miniature city, probably with as many as 5,000 people living there. In order to sustain this population, the Alhambra is threaded with gardens. The gardens of the Alhambra are designed to recreate an oasis. Don Antonio Malpica has studied the landscape of the Alhambra in depth. For him, the gardens have a dual purpose. In this sense, the sensation of being in a recreational space and at the same time a productive space is fundamental. So the gardens of the Alhambra were designed for practicality as well as pleasure. To grow food as well as flowers. There is just one problem. There is no source of fresh water on the Sabica hill. It's a huge drawback for a stronghold expected to feed and water as many as 5,000 people. The nearest water source is the river that flows just to the north of the site. But this has a severe drawback. Of course, if you'd been here in the 13th century, the river Darra would have looked pretty much like it does today. A small babbling brook making its way through Granada. The basic problem Mohammed has is that the water's down here and he needs it up there. To make the Alhambra viable, its builders must divert an entire river up onto the mountain of Mohammed. Making a river flow up onto the Alhambra is a huge challenge. But Mohammed and his engineers must find a way to make it happen. Because without it, he cannot transform his new citadel into a self-sufficient oasis of gardens and farmland. He needs to carry gallons of water to the gardens he's planning. To do this, he must thread the Alhambra with irrigation channels. And this is not an easy task. It's easy to forget in the modern world how significant water is in the historic environment, how difficult it was to get hold of. So if you imagine a community on top of a hill and a huge demand for water, hundreds of feet above the water supply that's most obvious, the local river. Of course, confronted with this, they do the obvious and clever thing really, which is to go up the river valley to some point where the water's actually above them and let the energy of the river itself bring the water to them. But there is no natural lake above the Alhambra, so they create one. Mohammed's engineers construct a dam above the Alhambra, which will build up enough water pressure to feed into the citadel. Six kilometres from the Alhambra, Don Antonio has found the dam that the engineers created. We find ourselves at the Río Darro, at the exact point where the first Nasrid king, Mohammed I, ordered the construction of a channel to divert water from the river. This dam creates a reservoir system capable of providing enough water to fill an Olympic-sized swimming pool every five seconds to the Alhambra far below. It's hard to believe that this was dug by hand almost 800 years ago, but beneath its modern concrete skin lies a truly ancient design. The water system has the same design as it had originally. The only thing that has changed is the building materials, because every year they had to renovate the channel and its outlets. There are two floodgates up there. One of the gates allows water to flow into the river Darro on the opposite side of the dam. The other channels water into the reservoir. Water from this reservoir flows into a brick-lined canal, known as an acequía by the Muslims. This ultimately feeds the Alhambra. But diverting the river Darro is just the start of this mammoth project. The canal builders still have to overcome a major obstacle. The reservoir sits in a valley between three hills. So in order to reach the Alhambra, Mohammed's engineers need to build a water channel six kilometres long that winds through the hills above the fortress. This has to carry the equivalent of 7,000 Olympic-sized swimming pools every day to support the Alhambra's growing population, and will only work if it flows downhill at a constant gradient. So how can this happen when there's a hill in the way? Their solution is a bold one. Instead of going over the high ground, they decide to go through it. The builders dig a tunnel about one metre wide and two metres high through the hillside towards the Alhambra. And the natural stability of the Alhambra conglomerate ensures that there's no danger of collapse. It must have taken them months to burrow a channel into the hill next to the Alhambra, known as the Heneralife. But there is still one great problem that must be solved. The Alhambra sits on a completely different hill. Mohammed's engineers must find a way to get the water from one hill to another. To get water from the hill of the Heneralife next to the Alhambra into the Alhambra itself, Mohammed's engineers need to cross a 15-metre gap that separates the two hills. The solution? An aqueduct. And this is where the water from the Darrow River arrives at the Alhambra. It comes across here. And in the old days, it used to go across the Acequía Real, which was the channel which took it all the way into the centre of the Alhambra. The Acequía Real formed the lifeline for the Alhambra's citadel. From here, water flowed to every part of the Alhambra. It provided fresh water for the populace and it fed the multitude of water features in the gardens of the sultans. These gardens were designed to symbolise the kingdom of Granada, over which the sultans ruled. The gardens had a practical function as well. They were designed to create an oasis in the heat of the Granada sun. Islam originated in the desert in an environment where water was at a premium and the ability to provide water and to have water flowing is naturally something that's extremely desirable. In fact, it's more than desirable. It's of crucial importance. Flowing water is very important from a Muslim perspective because you need it to perform ritual ablutions. And we'll notice in the Alhambra that water is rarely completely still. Even when you have still pools, water is flowing into those pools and flowing out again. And this is very important in terms of ritual purity, that all water sort of continues flowing. So, to keep the water pure, Muhammad's engineers must create a system that will prevent sediment from silting up the channels. Their ingenious solution can be found dotted all over the Alhambra. Shallow pools designed to slow the water down. Essentially, the water's coming, zooming down the channel, carrying all the bits and pieces and comes to an area where it's wide and deep and the water slows right down and the silt and sand is able to slow down and fall to the bottom. In this way, the water for the Alhambra's gardens will be kept constantly fresh. But too much water can be a bad thing. If the system overloads, it can back up, blocking the channel and stopping the water from flowing freely. To prevent this from happening, Muhammad's engineers decide to install a safety valve. Any excess water that might overload the Asikiyah is funnelled along a side channel that diverts it into an overflow system built into the walls. And this is where it comes out. The water starts off up in the Alhambra, comes down in a pipe, through this outfall, down this channel and joins up with the River Darrow again. The engineers may have ingeniously solved the problem of too much water, but not the problem of too little. And it soon became apparent that during dry seasons, the Alhambra could exhaust its water supply. At the summit of the Henir Alefe stands their solution to the problem. A massive set of reservoirs. These are positioned on the high ground so that gravity can ensure a constant flow of water to feed the gardens. To get the water up to these reservoirs, Muhammad's engineers harness a donkey to a mechanism of interlocking wooden gears. When it walks in a circle, it turns a horizontal wheel. This in turn rotates a gear attached to a water wheel which dips a line of buckets into the Asikiyah below and deposits the water into a reservoir above. In this way, the Alhambra's engineers were able to realise Muhammad's dream of an oasis of gardens surrounding the palace complex protected by his fortress. But Muhammad himself will not see this dream come to fruition. He dies in 1273 before his life's work is complete. Behind him, he leaves one great project unfinished. The prime reason he has built a fortress here in the first place, the Nasrid Palaces. This is the heart of the Alhambra. In the 100 years that followed Muhammad ibn Nazir's death, his successors completed the great perimeter wall that surrounds the citadel and began to construct the palace complex that would house his dynasty. Each palace is unique, built one after the other by a succession of sultans. Each ruler tended to want to build a new palace or at least renovate existing palaces to make their own mark. So you end up with a sequence of different buildings which gradually fill up the space and gradually create a whole network of palaces within the Alhambra complex itself. Together, they form one of the most impressive palace complexes still standing in Europe today. This is what the Alhambra was designed to protect. But there is one particular palace designed not just to protect but to intimidate. 1333, a century after its foundation, Yusuf I comes to the throne of the Alhambra. He inherits the mantle of sultan at a high point in Granada's long-running conflict with the Castilian Christians who occupy much of Spain. The reign of Yusuf I in the early 14th century is sort of the first high point of the kingdom. Yusuf I allies with the Marina dynasty in North Africa and appears to be in quite a strong position vis-à-vis the Christian kingdoms to the north. Alongside his new allies, the Marinids, Yusuf launches an attack into Castilian territory trying to regain some of the land his forefathers have lost. However, Granada's ascendancy is short-lived. Just seven years later, King Alfonso of Castile defeats the Muslims at the Battle of the River Salado forcing Yusuf's allies, the Marinids, to withdraw from Spain for good. This may explain why the last act of Yusuf's reign is to build a huge defensive tower, the biggest yet, on the Alhambra's north wall, the Torre de Comares. This massive tower stands 45 metres tall. It forms the centrepiece of the brand new palace that Yusuf decides to build. In order to shoehorn it into the new palace design, Yusuf's architects have to extend an existing tower on the north wall. They shift the existing sentry walk further north onto a new wall and extend the tower another 12 metres out. But Yusuf isn't thinking of defence. He's thinking of his image. His tower is designed to make a statement. Yusuf I has just suffered a terrible defeat. He decides to build a monument that will reinforce his power and invulnerability in the eyes of his people. By building this tower, Yusuf stamps his authority on his kingdom. But Yusuf isn't just trying to impress his own people. He wants to establish his invulnerability in the minds of his Christian enemies. The Great Hall in the Palace of the Comares is compensating, in a way, for a lack of military strength. Because he has to rely on political and diplomatic negotiations, he needs a very impressive space in which to conduct those. Today, thousands of tourists are overwhelmed by the same sense of awe that Christian ambassadors must have felt when they came to meet the Sultan, because the interior of the complex is designed to make an impression. This is Yusuf's Grand Palace. At its heart, the glory that is the Hall of the Ambassadors. Everything in this overwhelming room is designed to impress. Any visiting ambassador would have been struck by the sheer scale of the Alhambra. The entire edifice is calculated to convey an impression of supreme invincibility. The complex stucco work contains repeated Arabic inscriptions in praise of Allah. The most prevalent is the motto of the Nasrids, which is, there is no conqueror but God. And you see that repeated over and over and over again. The ceiling, 75 feet above, contains more than 8,000 individual pieces of cedar wood painted to resemble the seven heavens of Islam. The Comares Tower is a microcosm of the universe and the Sultan is in control of that. He is, in a sense, in control of the universe, which is quite a bold statement for him to make. Here lay the central challenge that Yusuf's architects had to face. They had to impress any ambassador who entered this room with the power and presence of the Sultan. To do that, they needed to focus all the attention in the room onto the Sultan's throne. It's a very striking manipulation of space to emphasise the fact that Yusuf I is a ruler of importance and power and that he is sort of in control of this kingdom. To do this, the Alhambra's architects had one thing that could help them. Mathematics. When the classical world collapsed, the mathematical knowledge used to build the great monuments of Greece and Rome was collected by Muslim scholars and passed down through the Muslim houses of wisdom to the time of the Alhambra. So all of the learning of the Greeks and later the Romans is incorporated into Islamic mathematics. They don't reject it because it doesn't threaten their religion. So here we have this classical legacy of mathematics that is not only inherited but then improved upon. Hispano-Muslim architects used a unit of measurement inherited from classical architecture called the Rashashid Kodo. It was about 62 centimetres long and virtually all of the Alhambra is based on this unit of measurement. This lay at the heart of the Alhambra's design. So to create a space that will overwhelm visitors with the importance of their sultan, Yusuf's architects design a ground plan 18 Rashashid Kodo square. They divide the room along its horizontal and diagonal axes. Using string, they mark out four 90 degree arcs from wall to wall. A straight line between the end points of these arcs creates an octagon. This allows them to create a larger square sitting diagonally across the original which marks the location of the central windows at the entrance. Equilateral triangles drawn from the centre of the walls create the perfectly proportioned width of these windows. It must have been a very intimidating experience to walk into the hall of the ambassadors and to see the sultan positioned there centrally commanding that space and arrayed behind him the panorama of his city and of Granada but also of his territory. So it must have been very impressive. It must have been calculated to intimidate. Forbidding both on the inside and the outside, the tower seems to have done its job. No one dared to attack the Alhambra while Yusuf was on the throne. In fact, Yusuf's downfall would come from a completely unexpected source. For with great beauty comes great pain. And before the Alhambra could truly flower, it would endure one of the most traumatic events in its history. 19th of October 1354, more than a century after the Alhambra's foundation, Yusuf I is preparing for his daily prayers. As he does so, he is attacked by a deranged slave. The madman stabs him to death. Yusuf was just 36 years old. His death paves the way for his heir, Muhammad V, to create what may become the Alhambra's greatest monument. Just five years into his reign, a court faction tries to assassinate the new sultan. Muhammad flees from his own people and seeks refuge with Granada's oldest enemy, the Christian king of Castile. Despite his nickname, Pedro the Cruel helps Muhammad win back his throne. Pedro the Cruel and Muhammad V clearly had a friendship which was based to some extent on shared intellectual and artistic interests. One could imagine that the two men could have had a genuine friendship beyond the politics of the era. And I think that just underlines the point that we shouldn't think of Christians and Muslims as always at loggerheads. His friendship with Muhammad will change the Alhambra forever. Like many Spanish kings, Pedro is profoundly impressed by the beauty of Muslim architecture. So when he builds a new palace in Seville, he models it on the Muslim pattern. And when Muhammad finally is returned to the throne and goes back to Granada, he spent several years in the company of another architectural fan discussing architecture and he brings many of the ideas that were developed in Seville back to Granada with him. This is very interesting because it means that the building that we consider the high point of Islamic architecture in Spain owes a debt to a Christian palace in Seville. When he returns to the Alhambra, Muhammad is determined to outdo Pedro's masterpiece in Seville and his triumphant response will be an architectural tour de force. With its magnificent courtyard and breathtaking ceilings, Muhammad V's palace will prove to be more beautiful, more sophisticated and more accomplished than the Muslim-style masterpiece of his powerful Christian neighbor. Under the reign of Muhammad V, the age-old rivalry between Granada and Castile takes a radically different course. Thanks to his friendship with Pedro of Castile, military confrontation transforms into an artistic competition. Muhammad commissions the exquisite palace and Court of the Lions which seeks to emulate and surpass the beauty of Pedro's palace in Seville. It represents a different part of palace more complex than the other ones because it has influences of both Islamic and Christian architecture at the same time. The Court of the Lions, for many people, is the high point of Nasrid architecture and the high point of Islamic architecture in Spain. It is spatially complex, luxurious, refined and it brings it all together in one exquisite space. Here is the crown jewel of the Alhambra, built according to a set of rectangles, each related to the other. Once again, Muhammad's architects use geometry to brilliant effect. When we look at the facade, what we see is a base width used to form a square which defines the next level up. Then we take the diagonal on that square, swing it through to the vertical. The point at the end of the diagonal hits the vertical becomes the next floor. We then do exactly the same on the diagonal from this corner. So what you're getting is a very precise relationship between one story height and the next in accordance with Greek rules. Now this looks right to us because the way that Greek architecture has come down to us defines our sense of beauty. We look at Greek buildings and they feel right to us because they're presented as beautiful artefacts. Despite these Western influences, the Palace of the Lions remains a resolutely eastern building. When we see it today, we don't really see it as it was. The four quadrants around the central fountain were actually sunken flowerbeds. The flowerbeds were encircled by the salons of the sultan's wives which overlooked the central garden. You would have had people sitting around the edges of the court on cushions or carpets looking out and just seeing the tops of plants and shrubs and trees. These rooms contain the palace's most spectacular treasure, an exquisite form of decoration known as moqarabes. It is absolutely unique to Islam. It's hard to explain where it comes from. It's hard to even understand it when you see it. It is so dazzling, it confounds the senses. You have a sense that it's not weight-bearing, that it's hardly there. It almost seems to move as you look at it because of the interplay of light and shade on these small stalactite-like elements. And again, it's mathematics that creates this astounding intricacy. There's an exact geometry to the pattern which uses triangles and rectangular blocks to create its effects. The variety of cuts in the plasterwork creates different geometrical shapes called adarajas. These are set into the wall of the building with clay ready for painting. The plasterwork is very complex, not only because the constant play between solid and void, but also it was originally painted. It was bright red, bright blue, so it would have been a very vibrant experience. The painters use exotic pigments, among them blue lazurite extracted from lapis lazuli in Afghanistan, which cost as much as gold. It's as if the rules of existence had been completely changed because overhead is this vault that you cannot comprehend. You actually cannot understand what the spatial dimensions are. There is no fixed point up there that you can focus your eyes. It is an extraordinary sensory experience. This was to prove the high point for the Muslim kingdom of Granada, because a century after Mohammed and Pedro's artistic alliance, a different kind of partnership would signal the Alhambra's downfall. In 1469, the Christian kingdoms of Castile and Aragon unite under Ferdinand and Isabella. Their historic alliance creates the kingdom of Spain and marks a brutal new phase in Christian policy towards Granada. The war they begin is a relentless crusade. On New Year's Day, 1492, after 10 long years of war, Granada, last Muslim bastion in Spain, finally capitulates to the Christians. Among those in the Spanish camp who witness the surrender is a sea captain seeking royal sponsorship for a voyage of discovery to the New World. His name is Christopher Columbus. The Alhambra's new Catholic masters would soon stamp their own mark onto the complex. In the centre of the fortress, King Carlos V began building a huge squat palace with a circular courtyard. It stands in marked contrast to the architecture of its Nasrid predecessors. Yet ultimately, nothing can detract from that exquisite beauty. If one compares the Alhambra with the cold, dank, stone palaces of Europe, it's just another world entirely. No wonder they wanted to conquer the Alhambra. It was absolutely beautiful and unlike anything that existed in Europe at that time. A fortress first, a pleasure palace second, and now a place of wonder for tourists from all over the world. The Alhambra still stands today as a testament to the genius and beauty of Muslim art and design.