The Citadel: Survival Under Siege | Documentary

Staggering. Imposing. Mysterious. In the 16th century, citadels were huge edifices, protecting towns and armies from invaders. Built at exceptional heights to repel enemies prepared to commit barbaric acts. Some have ramparts built directly on rocky ridges. It is quite a feat to get up there, but also to get the equipment up there, bit by bit, to build it. The results are astonishing, as here in Sisteron, a jewel in southeastern France. Other citadels were built to ward off the devastating attacks of new super-powerful cannons. In Besançon, the enemies had no idea that there was a gigantic, completely concealed protective wall. Imagine being bombarded from the hill on this side. Then the wall would protect the soldiers standing here, and vice versa. But citadels were also used to subdue the local population. Like Fort Saint-Nicolas, which had its cannons pointed at Marseille in case the people got rebellious. Louis XIV came to check out the Marseillais to see who's in charge. But the Marseillais weren't going to let that happen. They were even prepared to partially demolish it. The inhabitants used the stones to build their own houses. With its star shape, underground network of tunnels, and secure gunpowder store, which prevented the whole hill from exploding, Fort Saint-Nicolas still holds many mysteries. Sisteron, Marseille, Besançon. This is the story of the ultimate French citadels. From the 16th century onwards, when attackers wanted to take over a town, they only succeeded if they captured the citadel. The fortification perched over the town. The difference to castles is that they were also used as entrenchment camps for the population in the event of an attack. Citadels were almost exclusively military, to repel the enemy, and not intended as a retreat. When fortified castles gave way to these new citadels at the end of the Middle Ages, it was also because cannons and cannonballs had undergone a revolution. They were now made of iron, and could easily destroy the great outer walls. Citadels were built on rocky spurs, and had banks of earth behind their ramparts. Cannonballs were thus rendered less effective. These new fortresses were a turning point for the King of France. One of the constants of Louis XIV's reign was to mark the borders of the kingdom. Citadels allowed the royal troops to regroup at key points on the kingdom's borders in case of danger. Louis XIV also started building citadels to house the military. Before that, the garrisons that passed through the towns stayed with the locals. And one of the showpieces of this new city and its new type of buildings is the Citadel of Cisteron. In the department of Alpes-de-Haute-Provence, at an altitude of over 500 meters, the same height as One World Trade Center in New York, the Citadel of Cisteron stands out as a masterpiece. When you're up there, it's even more spectacular. It's amazing. It's the Citadel of Vertigo, and you can see it from a long way off. So we have a lot of visitors who pass by and see the Citadel and stop in their tracks. The Citadel of Cisteron impresses with its cliff-side walkways. Its chapel is exceptionally high, standing against a rock over an abyss. Its underground stairs are carved into the heart of the rock. It's the size of the first floor of the Eiffel Tower. Everything here is impressive and reveals absolute mastery of elevated structures. But the spectacular scenery is especially breathtaking. Two enormous rocks separated by a river, the Durance, the most important river in Provence. It's fed by the Alps, which aren't far away, and it is a significant waterway. The fractured landscape shows the power of this river that even the mountains cannot stop. The river was also a major challenge for trade. To the right of the Durance was the Via Domitia, a long Roman road begun in 118 BC. It was used by the garrisons protecting the cities that became Roman. It connected the Iberian Peninsula to Italy, and to the left of the Durance lay other trade routes. But between the two banks, there was no structure to cross the river. The problem was the power and current of the Durance, which no bridge could withstand. But how could a bridge be built over the Durance? A classic structure with pillars in the middle of the river wouldn't withstand the current. The solution was to span the Durance. And that was only possible because the distance between the two banks here is one of the smallest along its entire length. The great strength of this bridge is that the two pillars rest on two rocks either side of the river. In 1365, an arch with a 28-meter span was built. The total length of the bridge was 40 meters, with a width of six meters. An impressive structure. The bridge was a considerable asset for the development of Sistavon. More and more visitors came. But it also meant invasions. It meant conflict and wars. The wealth of a place or its development makes it attractive. The bridge thus became a gateway for all invaders. It was used in particular during the 100 Years' War. In 1337, England was in conflict with France and hordes of invaders overran the villages. They pillaged, they raped, they murdered. Henry IV decided to build this citadel to show that he was the king of all the French and to show that Sistavon was part of France and the citadel would protect Sistavon like its king. But back in 1589, building a fortress above the town on the heights of the rock was quite a challenge. Working at an altitude of 500 meters was difficult and dangerous for the stonemasons. They first had to assemble hundreds of tons of wood for scaffolding and gigantic arches that were used to build roofs. In particular, for one of the jewels of the citadel, the Church of Notre-Dame du Chateau. It was one of the first parts of the citadel to be built, combining military power with religion. And the builders weren't about to do things by halves. This church is remarkable. It looks like the chapel was born from this rock. The church sits on the side of a cliff, hanging on to the edge of the void. Architecturally, an audacious gamble. But why at the highest point? To build as high as possible is to get closer to the divine. But achieving this in the 16th century was very dangerous work. It was very complicated. The site was clearly not conducive to human settlement. An older church had once been built on the site. But the intention was to create a much more imposing building, requiring considerable work. With hammers, crowbars and pickaxes, the men set about building a plateau with an open space on three sides. The north side was left as it was, forming a natural wall against which the church could rest. The church is superbly constructed, but it has one drawback. You can't go round it. Part of it opens onto the void. If you opened a door on the south side, there was just a sheer drop. But what can be done to make the most of a terrace facing south? How do you gain more space? The answer is these impressive arches. They create more surface area above it. To build these arches, stones were raised about 30 metres. Then wooden scaffolds were placed on top. Next came stones cut millimetre perfect to enclose the semicircle. The last stone, placed in the middle, is the keystone. Once the scaffold was removed, the stones rested on each other, with gravity holding the whole thing together. Next, a platform was built just above these monumental arches. Notre-Dame du Château represents Gothic style with ribbed vaults. Just like with the arches below the terrace, wooden scaffolds resting on wedges at the top of the pillars allowed small stones to be laid to form the ceiling of the church. The building remained a place of worship for only a short time before being turned into a residence for the king's lieutenant at the end of the 16th century. Later, the chapel was even used to hold prisoners. For attackers, few missions were as dangerous as trying to take the citadel of Cistern because of its sophisticated defence system. It allows invaders no respite. Shots can come from all sides. Unlike the rectangular castles of the Middle Ages, the walls of citadels are much more complex and harder for attackers to penetrate. With their design, one wall above the other, defensive fire may come from anywhere. You also have to be able to get into the citadel, and Cistern has a particularly elaborate drawbridge system. The main flaw of drawbridges used to be that they are heavy and take a long time to build. But the fortress of Cistern has a completely new structure, a zigzag drawbridge. Thanks to its off-axis levers and its weight distribution, the bridge can be raised in a matter of seconds. Precisely calculated counterweights make it possible to lift the 900-kilo bridge with great ease. With two men, or just one, pulling on a chain, the bridge can be raised. Because of the geometry of the counterweights and the axles. This drawbridge had been destroyed, but after several years of research into its plans, an association had it rebuilt accurately. The decking, the passageway was all that was left. The mechanism was gone. After 20 years of work, the bridge could be restored along the same lines as when it was built. All the rivets were hot-hammered. We positioned the rivet, heated up, and once it's red-hot, it's hammered in on the other side so that the whole thing can be closed and nothing can move. The part is then completely solid. Even if invaders managed to cross the drawbridge in time, they were suddenly exposed and very vulnerable. And an easy target without being able to retreat. In order to see enemies coming from afar, an impressive walkway was built. The view is breathtaking, with a beautiful panorama of Haute-Provence. It's a bit dizzying, but the view is overwhelming. A 360-degree vista means nothing escapes the trained eye. And it's also ideally located 150 kilometers from both the Mediterranean and the Alps. Building such a rampart requires a great deal of skill. The ridge is irregular and gets thinner the higher it goes. So they used a sandwich technique, working on both sides of the ridge. Recesses were dug into the ridge's north and south sides. Perfectly cut stones could be placed at the top. It's quite a feat to climb it, but it's an even bigger feat to assemble the material, bit by bit, and construct it. Regarding the rock, they chose stones that were relatively solid in themselves. But if you look closely, there are layers, there are places that are a bit loose and others that are more compact. Once the foundation was built, temporary wooden platforms were added so that the wall could be extended ever higher. Entire plots of forest were felled to build this rampart, just like the rest of the citadel. You won't see wood in the citadel, but it was essential because it was used for construction. A level is erected along the entire length. Then the wooden scaffolding is raised. Another level of stone is added, and so on. The parapet walkway is one of the highlights of the citadel. But at the end of the Middle Ages, and later in the Renaissance, the citadel had to be able to withstand artillery armed with new cannons. Cisteron had to evolve, and it was one of the most famous military engineers of all time who demanded it, Sébastien Vauban. He was the architect who built the most fortifications in French history, which is incredible. Voltaire called him the greatest engineer and the best citizen. We know that he even went to the front. He took part in about 50 sieges, so he wasn't afraid to face danger. Vauban remained in the service of Louis XIV for half a century. It was one of the longest careers ever devoted to one sovereign. As an expert, he was sent to a number of citadels near the French borders. His mission was to consolidate them in order to secure the territory. When Vauban arrived at the citadel, he took a good look at the building and immediately found its Achilles heel. One of Cisteron's weak points was the powder store, a small building containing all the gunpowder for firing cannons. The magasin, as it's called, contained whole barrels of gunpowder and was positioned right in the heart of the citadel. If a cannonball were to hit the magazine, it would be the end of the citadel. Vauban decided to move the crates of gunpowder to the north, but still within the walls so that the soldiers could access them quickly. This is the store. It has very thick walls to contain the blast of an explosion, whether from outside or inside. The sides are made of stone, weighing several hundred kilos, but the vault itself is very different. It's made only of bricks. A brick vault, because in the event of a catastrophe, they wanted a vertical explosion, not a horizontal one. The concept was to contain the explosion horizontally, to allow it to escape as far as possible upwards. But the situation would still be problematic. Without a powder magazine, the citadel would no longer be able to defend itself. They had to make the building safe, but they also had to protect the powder against humidity. If gunpowder gets damp, it's unusable. To prevent this, horsehair placed in a case on the barrels acted as a hygrometer. If the horsehair curled, it was because there was too much humidity, so they could then air the rooms and reduce the humidity. Ventilating the powder magazine was essential, but installing windows would weaken the walls. Thus, Vauban opted for loopholes, but they were more complex than they seemed. Indirect openings were created, so that in cases of negligence, sabotage or attack, not everything could be blown sky-high. But despite all its technical innovations, over time, the citadel lost importance. As often happened in the Middle Ages, orders shifted and frontiers moved away from the citadel of Sisterol, so other places became more significant. This trend continued in the following decades. The citadel was no longer attacked. It did, however, undergo one last modification. Much later, in the 19th century, the fortress was turned into a prison, and its inmates left an astonishing legacy. It's a staircase that was built by prisoners held at the Sisterol citadel during that time. You can imagine that the working conditions were very harsh. The staircase leads from the citadel to the northern gate of the town at the very bottom, impressively breaking through hard rock over a length of more than 100 meters in height. An absolutely colossal construction site, a 258-step staircase that was dug out with digging bars. The conditions must have been absolutely terrible. Classified by UNESCO, preserved and restored, the citadel has become a tourist attraction. 80,000 visitors a year discover the mysteries of its construction and explore eight centuries of history. In a fascinating, immersive experience. Something it shares with another equally breathtaking monument, the citadel of Berzoncon. This is the citadel with all the records. 1.8 kilometers of ramparts, an area the size of more than 10 football pitches, architecture made for war. And if Faubourg's contribution to Sisterol was ultimately discreet, Berzoncon was one of his finest works. Of all the fortifications he built in France and Europe, he called this his ultimate citadel. Ultimately, the purpose of a fortification is peace, not war, so you have to make an impression. And here, the architecture does just that because it's on a rocky spur, very visible, and it dominates the whole area. A perfect citadel with a masterly defense. Located in Bourgogne-Franche-Comté, Vauban made it an absolute strategic site after having conquered it himself during a siege. The history of the Berzoncon citadel is an adventure story in itself. One that goes back 2,000 years to antiquity. On discovering the site, Julius Caesar saw the possibility of using it as a stronghold for his army. When Caesar conquered Gaul, he identified sites that offered good natural defenses and thus required little work. So if you have a waterway that forms a loop, all you have to do is build additional fortifications and your site is protected. Indeed, the whole old town of Berzoncon is concentrated in a loop, so of course, strategically, it's very easy to defend the city. And nature lends another helping hand. A hill closes the loop, Mont Saint-Étienne. From Caesar to Vauban, it was to take a very long time for a fortress to be built on this hill. And it was Louis XIV, the King of France, who demanded a citadel in Berzoncon. Even though the region wasn't part of his kingdom at the time, the sovereign, by playing a game of alliances, planned to gain the territory in order to expand. In 1668, the Marquis de Louvois, one of Louis XIV's most important statesmen and his principal minister, spoke to Vauban. He told him that the King wanted a citadel in Berzoncon and gave Vauban the task of designing it. So on his arrival at the beginning of March, 1668, Vauban took his team around the hills and said, we're going to build the citadel here on Mont Saint-Étienne. All the stone used came from Mont Saint-Étienne, where the citadel itself was built. The ditches, the trenches, the underground tunnels, all dug to create the almost two kilometers of ramparts. Wherever he worked, Vauban adapted. He was really good at exploiting local resources. The result is impressive. With ramparts as high as six-story buildings, set on a rocky spur, itself 100 meters high. It's extremely vertiginous, and it's so well placed on the cliffside that today we have a variety of species that use both the cliff and the wall. A lot of birds are born in the ramparts throughout the year, and they end up confusing the stone with the cliff. If this is one demarcation between rock and stone, there's another, even more surprising one. The highest part of the ramparts isn't made from the rock of Mont Saint-Étienne. It's made of brick. This is one of Vauban's trademarks, and bears witness to his personality. Vauban was very concerned about the health of the soldiers, so he wanted them to be well-fed and protected. They weren't just cannon fodder for him. When a cannonball hits a stone rampart, the shrapnel is usually large and very sharp. Nearby soldiers could be killed or seriously injured by large pieces of stone. But if a cannonball hits a brick wall, the debris is much smaller and not as sharp as stone. The brick absorbs shocks and crumbles, so it's much less dangerous to hide behind it. For Vauban, the lives of his soldiers were more precious than anything else. He was also very attentive to small details. Like, for example, he worked on a new wheelbarrow, which would be more efficient to carry rocks during construction. He had real attention to detail. He even came up with a recipe for soup for the soldiers. To protect his men and the citadel, Vauban decided to build half-moons. Polygonal structures that eliminate blind spots. The faces are at an angle and respond to each other symmetrically. On the half-moons, you can see the embrasures that correspond to where the cannons were. Not every embrasure corresponded to an artillery piece. There were, in fact, far fewer. It was mainly to impress the enemy, and the guns were positioned where they were needed, depending on where the enemy was. When enemy forces arrived, they were inevitably under fire from two or more angles. A large number of invaders could overwhelm a half-moon's defenses, but the layout of the citadel is intended to slow down the attackers, and their route was then a complicated one. Vauban thought of everything. Even if the enemy managed to take the half-moon, then there was a drawbridge that prevented them from going to the next front. The ditch is almost 20 meters wide. There's no water, just a ditch to prevent the enemy from passing, and above all to channel them onto this drawbridge. In the event of an attack, one could then raise the bridge or destroy it. The ditch also serves as a quarry for other structures. Vauban wanted Besançon to have solid defenses. The city had to have its own ramparts. But that wasn't enough in the event of an attack. So Vauban had the entire city walls built with an innovative structure. The bastion towers were created specifically for Besançon. These towers protrude slightly into the river and were intended to defend the whole perimeter of the loop of the Doubs and the old town. The six towers were completed in 1693, providing the city with improved protection. 100 meters higher up, the citadel was being developed, and some of it was spectacular, like the great transverse wall. It's invisible because it's encompassed by a gigantic barracks called the Cadet Building. It's over 200 meters long. It's one of the most important structures in the citadel, a huge wall that divides the fortress into two parts. There are only two facilities like this in Europe. The soldiers could take refuge on one side of the wall or the other. So if the citadel was being bombarded from the hill on this side, the transverse wall would protect the soldiers here and vice versa. At three meters thick, the transverse wall provided excellent protection against the cannonballs of attackers. On the front line, it wouldn't have lasted long. The cannons of the time were so powerful that Vauban had to find a way of defending the structures of the outposts. This is the very principle of these citadels, which replaced castles, which have become too fragile, their high walls offering insufficient protection. Huge earth embankments were piled up behind the limestone ramparts. They looked like they were pushing against the rampart. And if a cannonball hit the wall, the embankment absorbed the energy. Earth absorbs shocks in a way that no building can. Using it this way was a great advance in the configuration of these citadels. To build the embankments, as much earth as possible had to be collected from the surrounding area and packed in tight behind the ramparts, a colossal task that Vauban was used to fulfilling. But one of his other constructions seems to have gone completely awry, a gigantic hole that required considerable effort to dig the well of the citadel. Its depth is exceptional. It's one of the deepest wells in France. The well is 132 meters deep. With only digging bars to work with, the builder's achievement is mind-boggling. At the time of construction in the 17th century, it was pure manpower. This was before the Industrial Revolution. Manpower did the excavation and made the well possible. We don't know how many men Vauban needed to meet such a challenge, but one thing is for sure. Once the water table was reached, the disappointment was immense, as the water from the well was unusable. It was never used. The water it supplied was of poor quality. It was brackish and thus unsuitable for the inhabitants, even for the animals that were kept there, like horses. The water was absolutely undrinkable for fish humans and animals alike. The only pitfall of this impressive citadel in Besançon. But even if Vauban's plans went as he intended, the architect wasn't happy. In the space of a few years, Besançon moved several times from one kingdom to another without being able to do anything about it. The city's population was fed up with these constant changes, anger was growing. You never knew whether the population would rebel, so they needed to be kept under pressure. To this end, the cannons were directed towards the city. If the town rebelled, they would set fire to it. However, this strategy revealed a problem. The citadel's artillery was limited in range. The effective range of a cannon in those days was just 600 metres. Half the city was under threat. The other half would have plenty of time to organise and revolt. So Vauban decided to add one last unplanned construction, and not just another rampart or new tower. He built a fort at an ideal location. Fort Greffon stands right opposite the citadel. The two fortifications complement each other. Fort Greffon is just over one kilometre from the citadel. With its cannons facing the city, it fills the gap to put the city under pressure. That dealt with the last 600 metres. Vauban knows that with this additional fortification, he's in an excellent position to suppress any desire for war on the part of the population. Woe betide anyone who lived next to St Peter's Church. They'd get it from both sides. Fort Greffon marked the end of the titanic enterprises at the citadel. The complex was finished, a masterpiece of fortification, but also a drain on Louis XIV's finances. It was very, very expensive, but in the end, it kept the peace. So was the cost that important? And today, it's an asset. A coveted jewel, taken from France on just one occasion. At the very beginning of the German occupation during the Second World War, the Nazis made it one of their strategic bases. The Germans took possession of the citadel and unfortunately used it to execute resistance fighters. And during the war, we had bombs dropped by the Nazis. The bombs were dropped by the Allies at the time of the liberation of Besançon. But the bombs didn't destroy the citadel. And thanks to conservation measures, the Besançon citadel is now a major attraction for the region. Listed by UNESCO, every year, 280,000 visitors come to this unique site. And it has one very special feature, a zoo. With tigers, tiny monkeys and dozens of endangered species that the keepers take great care of. 600 kilometres away, other teams have also done admirable work. They've restored a military site that has been closed to the public for over 300 years. But today, the citadel of Marseille is finally opening its doors and revealing all its secrets. Situated in the heart of the city, it overlooks the old port. It was built in record time, between 1660 and 1664. The result is astonishing. If you fly in from the Mediterranean, passing over the Chateau d'If, made famous in the Count of Monte Cristo, and climb high enough, you can clearly make out the building. It's star-shaped. A citadel commissioned by the young French king, Louis XIV. He was only 22 years old when he arrived in Marseille in 1660. The citadel would become a formidable weapon to control the city. Just as he later did with the citadel of Besançon. For five years, the people of Marseille have been resisting royal authority and power. And then there's also the context of national rebellion, with the nobility against Louis XIV. But it took more than that to discourage Louis XIV and his ambition. He wanted a strong kingdom. And he was full of confidence. He had just signed the Treaty of the Pyrenees and put an end to the Spanish war. The king arrived in Marseille a conqueror, confident of his ambitions. He wanted to impress Provence and show off his power. It was the king's will. The future Fort Saint-Nicolas, named after an old chapel on the site, would have its cannons trained on the city. If Marseille didn't want the kingdom of France, then its fate would be to end in fire and blood. To implement his will, he hired one of the great masters of fortification. Everyone thinks it's a Vauban fort, because it has the characteristic shape of the Bastion forts popularized by Vauban. But it was actually built by one of his predecessors, Louis-Nicolas de Cléville. The engineer of the king's fortifications was quick to find a high point, the basis for many citadels. He chose this 50-meter high spur, with an unrestricted view over the city. But ultimately, the fort was too strongly oriented towards Marseille, and not enough towards the sea. In the event of a sea attack, the citadel would not be effective. Its cannons were too far from their targets. There was only one solution. Build another fort dedicated to potential threats from the sea. Fort Saint-Jean. The two fortresses combined promised hell for anyone attacking the city or rebelling against the kingdom. The site was approved by de Cléville, but the fort had to be built quickly. There was dissent in the town, and the perceptible threat of a revolt. So the engineer went to great lengths, and was assisted by the king, who landed in Marseille with 7,000 men. Work began just over a month after his arrival. At a height of 50 meters and covering 5 hectares, the equivalent of seven football pitches, Fort Saint-Nicolas started to take shape. The stones used came from a quarry renowned in the region for its quality. La Couronne, just 30 kilometers from the city of Marseille. The limestone found there is very dense, very hard, with a pretty pinkish color. It arrived by boat, the best means of transport for deliveries of several tons a day. It's almost a square, a fortified castle with four towers, but with four-pointed bastions and a half-moon protecting the entrance. This shape, inherited from the Italians, makes it possible to fire from several different directions, and also defend against cannon fire more effectively. This first star-shaped construction was followed by a second, encompassing it. Three additional half-moons were built, giving the citadel a totally impregnable, even aggressive appearance. Not to mention its imposing edifice and wide ramparts. It's like a sandwich. There are walls made of stone and filled with rubble and mortar to make the ramparts really solid. The walls are up to two meters thick. It's fantastic to see such a monumental building and know that it was built in only four years. Other imposing structures include the powder magazine, which stored barrels of gunpowder for the fort's cannons, but also presented a massive danger to the fort itself. To secure this highly sensitive site, the builders gave it a unique structure. While the walls are made of ashlar, the roof consists of three layers. Two layers of brick, separated by another essential layer. Between the brick layers, there's earth. If there's an impact, the powder magazine would collapse. And the earth would smother the powder. But that's not the only special feature of the powder magazine. Here in Marseille, it has decompression chambers under the floor. We discovered two cisterns running the length of the powder magazine and we wondered what they were used for. Was there water in them? Were they used to store equipment? In fact, our research showed that the cisterns were air-filled and their purpose was to act like a decompression vault. If the powder magazine was ever attacked and exploded, the impact would be absorbed by the ground and would allow the powder magazine to implode rather than explode and damage the citadel. The powder magazine never needed to use its tanks. It remains in an authentic state of preservation. The same cannot be said for the ramparts of Fort Saint-Nicolas. More than a century after its construction, it came under attack from the people of Marseille. As an emblem for royal power, it was taken during the revolution by the people of Marseille, who considered it their property. In May 1790, the French Revolution reached Marseille and this symbol of the monarchy. They destroyed the eastern part of the ramparts and the northern part. Once the fury had died down, Fort Saint-Nicolas was in a bad state. So much so that the people of Marseille no longer had respect for the citadel and its function continued to be undermined over the years. The inhabitants used the stones to build their own houses. Over the coming decades, Fort Saint-Nicolas was on the verge of being completely destroyed. But in the 19th century, a decree banned the people of Marseille from entering the citadel. It could still be used by the army, provided it was restored. A restoration which went even further than planned. The citadel today is very different. You can clearly see the outline of the ramparts. The original La Couronne stone marks the limit of the demolition and everything above that is from the 19th century. That quarry had been closed and so for the restoration, the military had to use stone found on the site. Rubble that clearly shows the difference in construction. But the restoration work didn't stop there. The state decided not to base the new citadel on the design of the old fort. It would have to be much higher in the 19th century than in the 17th. But why increase the height of the walls? Developments in military technology had changed the idea of what a citadel should be and how it should defend itself against new artillery. A ballistic study revealed that the range of cannonballs increased from 300 to over 1,000 meters in the 19th century. With the advances in weaponry, if you fired a cannonball in 1820 from Fort Saint-Jean or Notre-Dame-de-la-Garde, it landed inside the high fort and then the fort would be finished. It wasn't just the visible structure that was modified. Inside the rock itself, there is a network of underground cavities. It's like a Swiss cheese. An underground network of tunnels that allow the governor, his major or his lieutenant, to leave the citadel discreetly. These tunnels were then used by the Nazis during the Second World War occupation and later by French intelligence. They served as a base for secret agents to collect sensitive information about the city from the very heart of the rock. Well-hidden structures. And maybe not the only ones. The fort is vast. There are still a lot of things left to discover. Since 2024, the people of Marseille have had the chance to discover the secrets of the citadel. Civilians were forbidden from entering the site for over 350 years. After serving as a citadel and barracks for almost a century, Fort Saint-Nicolas was also a prison. It wasn't until the early 2000s and the start of 20 years of restoration work that the challenge of restoring this monument to the city could finally be fulfilled. The Marseillais tell us it's incredible. We never imagined it was so huge, so phenomenal, we forgot about it. Now, I think everyone will be able to rediscover it. The citadel has become a jewel of the city its inhabitants can now enjoy to the full. It's one of the landmarks that make up the world's heritage. With Besançon and its insuperable position. And Sistre, a stone colossus at the top of a mountain. France is doing its utmost to keep its legacy intact. Open to the public, the citadels take us back to a time when towns were so vulnerable that fortresses were built to protect their citizens. And also, sometimes, to keep them in check. For the future, they remain unique masterpieces of human engineering and the genius of their builders.