The art of defense in war is epitomized by the fort, whether simple wooden stockades or elaborately engineered complexes of walls, ditches, and towers. Throughout history, the defender has struggled to be one step ahead of the attacker’s tactics and weaponry. The results can be seen in many ingeniously designed fortresses that made invaders pay dearly for their capture.

The list below gives ten examples of such fortresses, ranging from the merely strong to the invincible.

Related: 10 Really Surprising Facts About Ancient Warfare

10 Masada

The Defenses: What made Masada almost impregnable was the sheer height of the isolated plateau on which it stands. The rock rises 1,424 feet (434 meters) from the arid desert floor southwest of the Dead Sea. It was further fortified by the Hasmoneans in the 2nd century BC before Herod the Great took it over as a site for his palace.

Herod surrounded the perimeter of the mesa with a 4,500-foot-long (1,372-meter) defensive double wall close to 20 feet (6 meters) high. The wall was punctuated by more than 30 towers and four gates. The aqueducts he constructed brought 200,000 gallons (757,082 liters) of water to the cisterns and, with the numerous storerooms stocked with food, assured that 10,000 defenders could survive for months.

Was It Conquered?: After the fall of Jerusalem during the great Jewish revolt, rebel remnants continued to defy the Romans from atop Masada. The Roman Xth Legion was dispatched to take the stronghold in AD 72. Nearly 15,000 Romans besieged a thousand Jews, including women and children, by building a ramp of stone and earth where they could wheel the siege engines to the summit. Once there, they were able to breach the wall. Rather than give the Romans the satisfaction of enslaving them, the garrison committed mass suicide.^[1]

9 The Theodosian Walls

The Defenses: After the empire’s capital was moved to Constantinople, Roman emperor Theodosius II set about building its defensive walls, which were continually improved upon through the centuries. The enemy’s first obstacle was a ditch 65 feet (20 meters) wide and 23 feet (7 meters) deep that could be flooded with water. After this was an outer wall, then a second wall with towers and firing platforms.

Further beyond was a third wall 16 feet (5 meters) thick and 39 feet (12 meters) high, with 96 projecting towers, each capable of holding three artillery pieces. This entire complex was built on a rising embankment, and the plan made it impossible for siege engines to approach the inner wall. From these formidable defenses, the defenders could rain down their secret weapon—Greek fire—on the attackers.

Was It Conquered?: For 800 years, Persians, Slavs, Avars, Rus, and Bulgars all pounded their heads against the walls to no effect. In 1204, the Fourth Crusade captured Constantinople, but only because a gate had been carelessly left open. The city was restored to the Byzantines, but the empire was already in decline. When Ottoman Sultan Mehmed II came to take Constantinople in 1453, it was defended by only 7,000 men against a force of 50,000 to 80,000.

Mehmed brought with him the largest cannons the world had yet seen. The mightiest, the Royal Gun, needed 60 oxen to pull and 400 men to maneuver. Its stone shot weighed 1,500 pounds (680 kilograms). But even with such massive firepower, Mehmed found the defense so frustrating that at one point, he was ready to give up and offered to lift the siege if the Byzantines agreed to pay tribute. They refused, so Mehmed continued his ceaseless pounding until the walls finally gave. The Ottomans had retaken Constantinople after 53 days of merciless battering.^[2]

8 Kenilworth Castle

The Defenses: Began in the late 11th or early 12th century, Kenilworth in Warwickshire is known primarily for its water defenses and walls-within-walls enclosure. From an original motte and bailey timber structure (a motte is an elevated area of ground dominated by a keep; a bailey is a walled courtyard), Kenilworth evolved into a stone castle further strengthened by King John from 1210 to 1216.

The Great Keep was provided with “fishtail” slits, an innovative design that allowed the firing of crossbows. The brooks nearby were dammed, creating an artificial lake: the Great Mere. Protecting all sides of the garrison except the north, the lake, the largest artificial water barrier in England, made the castle nearly impossible to take.

Was It Conquered?: In the uprising of the barons against King Henry III, Kenilworth, then in the hands of rebel Simon de Montfort, was besieged by royal forces from June to December 1266—the longest in English history. Prince Edward tried to crack open the defenses with heavy trebuchets and nine or eleven siege engines to no avail. Even a nighttime waterborne attack was stymied by the Great Mere. In the end, not military force but disease compelled the castle’s surrender.^[3]

7 Mont St. Michel

The Defenses: Mont St. Michel’s location is forbidding enough. Built on a rocky tidal island off the Normandy coast, it can only be reached on foot at low tide. And the tides are strong and dangerous, with a 50-foot (15-meter) difference between highs and lows being normal. Sometimes, tides change so quickly that they turn the bay into quicksand. As if nature wasn’t enough of an obstacle, French kings Philip II and Louis IX further strengthened the island with defensive and exterior walls.

Was It Conquered?: Mont St. Michel’s defenses were continually upgraded during the Hundred Years’ War. The chancel of the church collapsed during the terrible siege of 1421, but otherwise, the citadel, defended by only a few knights, survived English attacks for 30 years.^[4]

6 Krak des Chevaliers

The Defenses: Situated near the Syria-Lebanon border in what was once the Crusader county of Tripoli, the Krak incorporated the latest engineering techniques in 13th-century castle construction to keep up with the greater firepower of besieging armies in the form of counterweight trebuchets. These included more massive towers and thicker double walls with sloped outer bases to make them harder to breach.

Machicolations, loopholes, arrow slits, and “murder holes” were protected openings that allowed defenders to rain missiles on the enemy without exposing themselves. The Crusaders smoothed out the rock summit on which the Krak stood, denying attackers any handhold or foothold. The main gateway could only be reached via a hairpin bend, considerably slowing down the enemy. Ingenious changes in lighting levels wrought havoc on visibility.

Was It Conquered?: In 1271, the Muslim Mamluk leader Al-Zahir Baybars besieged the Krak. His catapults destroyed one of the outer towers, and two weeks were needed to breach the inner wall. The surviving few Knight Hospitallers held on for an additional 10 days in the largest tower of the inner wall until a forged letter allegedly from the Hospitaller Master instructed them to surrender.^[5]

5 Kumbhalgarh

The Defenses: Located in Rajasthan state in northern India, Kumbhalgarh is surrounded by mountains 3,560 feet (1,087 meters) above sea level. The defensive walls total 20 miles (32 kilometers), with widths varying from 15 to 25 feet (4.5 to 7.6 meters). This was enough, it was said, to allow eight horses to run side by side.

Access is through a series of sharply turning ramps that are difficult to negotiate. Seven imposing gates with colossal iron doors studded with spikes awaited attacking elephants. Even if the enemy made it through, they had to navigate narrow passages and five-foot-high (1.5-meter) doors, not to mention the numerous confusing traps inside the fort.

Was It Conquered?: Since being built in the 15th century, the present fort had been invincible through numerous attacks. Finally, in 1576, Emperor Akbar’s treacherous general, Shahbaz Khan, resorted to poisoning the water supply. Finally, the defenders of mighty Kumbhalghar had to surrender or die of thirst.^[6]

4 Hochosterwitz

The Defenses: Nestled on top of a 564-foot (172-meter) dolomite rock in the Austrian province of Carinthia, Hochosterwitz Castle can only be reached via a winding path blocked by 14 fortified gates. Any attacker had to capture each gate in succession, all the while being ambushed by defenders from the sides. Aside from this main defensive feature, the castle has the customary square tower and walls.

Was It Conquered?: The gates were constructed between 1571 and 1600 in the age of Turkish incursions into Austria. The Ottomans attempted to take the castle but were never able to get past the fourth gate. Hochosterwitz proved invincible and remains in the possession of the same family to this day.^[7]

3 Castillo de San Marcos

The Defenses: Built by the Spanish between 1672 and 1695 at St. Augustine, Florida, San Marcos is the oldest existing seacoast fort in the continental U.S. With the advent of gunpowder, fortress design had undergone a revolution to remedy the vulnerability of traditional square strongholds to cannon fire. The star-shaped bastion, like the one at San Marcos, minimized the surface area a cannon shot could hit perpendicularly and with force. Moreover, defenders had a greater arc of fire on the enemy, and those who reached the walls could be raked by fire from the sides and rear.

But San Marcos had an added bonus: the walls were made of coquina, a local limestone found along the coast. Created from the shells of coquina clams, the stone contains millions of microscopic air pockets, making it compressible. The Spanish were not aware of this at the time, so they made the walls 35 feet (10.7 meters) and 12 to 19 feet (3.7 to 5.8 meters) thick to offset what they thought was the liability of using soft stone. A surprise was in store for them and the enemy.

Was It Conquered?: British forces from South Carolina laid siege to St. Augustine in 1702, burning the town and bombarding the fort. But instead of pulverizing its walls, British shells were either deflected or harmlessly buried themselves into the soft rock. The porous nature of the coquina simply absorbed the cannonballs. After 50 days of such futility, the British gave up.

They tried again in 1740 with the same result. San Marcos was never taken by force. It was ceded by treaty to the British after the Seven Years’ War.^[8]

2 Murud Janjira

The Defenses: An oblong fort on an island in the Arabian Sea, there was no way to approach Janjira but by the sea. Any enemy would then have to contend with 40-foot (12-meter) high walls with 19 bastions defended by more than 500 strategically placed cannons. These include three of the largest cannons in India, with the heaviest, Kalal Bangadi, weighing 22 tons and could reportedly fire a projectile up to 7 miles (12 kilometers).

Was It Conquered?: The Maratha ruler Chatrapathi Shivaji attempted to take the fort thirteen times between 1659 and 1678 but failed. His son Sambhaji tried building a causeway from the shore to the fort. He was on the verge of capturing it until he was distracted by an attack on one of his own forts and was forced to retreat. Even the superior firepower of the Portuguese, Dutch, and British was no match for Janjira. The fort was never conquered.^[9]

1 Switzerland

The Defenses: Put simply, the entire country is a fortress, protected on all sides by towering Alpine mountains. Called the Swiss National Redoubt, it is a complex of bunkers, tunnels, shelters, warehouses, and other military installations hidden within the mountains. During the Cold War, roads, bridges, and railroads were rigged with explosives to ensure their complete destruction and make them useless to any invader.

Mountainsides along roads were also booby-trapped to trigger artificial rockslides. The entire populace could hide in thousands of bomb shelters for long periods. In addition, all able-bodied males to this day have military training. In World War II, they were instructed, in the event of a German invasion, never to surrender and, if necessary, flee to the mountains and fight individually.

Was It Conquered?: The Nazis’ contempt for “the stinking little state” prompted Operation Tannenbaum, the plan to invade Switzerland. But realizing the costs of subjugating the country deterred them from realizing the plan. No one has since dared to mess with the Swiss.^[10]

Medieval fortresses stand as silent sentinels, shrouded in a veil of ancient mystery and awe. These formidable structures, dotted across the landscape of history, hold within their stone walls the echoes of a bygone era. From towering castles perched on hilltops to sprawling fortifications guarding strategic positions, these fortresses were the bastions of power and defense during the Middle Ages. Their significance transcends mere architectural marvels as they encapsulate the triumphs, tragedies, and enigmatic secrets of a turbulent past.

As we embark on a journey through the labyrinthine corridors of medieval fortresses, prepare to be captivated by the untold tales and hidden whispers that have withstood the test of time. Behind every mighty gatehouse and impregnable wall lies a tapestry of secrets waiting to be unveiled. From tales of treacherous plots and covert passages to inexplicable disappearances and hidden chambers, these enigmas beckon us to delve deeper into the annals of history.

Unlocking the mysteries of these ancient fortifications allows us to unravel the untold stories and immerse ourselves in the intrigues of an era long gone, awakening our sense of wonder and fascination for the unknown. Join us as we uncover the ten secrets that lie within the heart of medieval fortresses, and let the whispers of the past guide us on this captivating journey of discovery.

Related: Top 10 Mysterious Skeletons Found In Castles

10 Ingenious Plumbing Systems

Within some ancient medieval fortresses, a hidden secret lay beneath the grandeur—a sophisticated plumbing system that operated behind the castle walls. These ingenious systems encompassed toilets, drains, and sewage disposal, showcasing the remarkable advancements of the time. The plumbing systems were intricately designed, with underground channels and flushing mechanisms that contributed not only to the castle’s hygiene but also to its defense. The medieval architects and engineers employed their ingenuity to create networks of pipes and conduits that efficiently managed waste and ensured a more sanitary living environment within the fortress.

The medieval plumbing systems were a testament to the resourcefulness and engineering prowess of the time. They enabled the fortresses to maintain cleanliness and hygiene standards, crucial for the well-being of the inhabitants. Whether it was the use of latrines that directed waste to castle moats or rivers or the implementation of internal castle channels for waste disposal, these systems played a vital role in upholding the castle’s functionality and overall defense.

The mysteries surrounding the design and construction of these intricate plumbing systems leave us in awe of the medieval craftsmen who brought these innovations to life, hidden within the ancient walls of the fortresses and shrouded in a sense of mystery and fascination.^[1]

9 Hidden Passageways

Many medieval fortresses harbored enigmatic secrets concealed within their stout walls. Hidden passageways, known only to a select few, played a crucial role in the strategic defense and escape mechanisms of these imposing structures. These covert routes provided defenders with the means to navigate undetected or flee during sieges, confounding their adversaries and turning the tide of battle. Such clandestine tunnels and corridors formed an intricate network, ensuring the survival of those within the fortress and serving as a testament to the ingenuity and resourcefulness of medieval castle builders.

Medieval fortresses have intrigued generations with their enigmatic allure, captivating imaginations and evoking a sense of mystery. These architectural marvels incorporated hidden passages and secret chambers, each with its own purpose and intrigue. These concealed spaces held valuable insights into the lives and concerns of castle inhabitants, revealing glimpses of a bygone era and the challenges they faced.

The hidden passageways of medieval fortresses stand as a testament to the secrets of the past, whispering tales of bravery, survival, and the timeless allure of the unknown.^[2]

8 False Entrances

Ancient medieval fortresses harbored intriguing secrets, including deceptive entrances designed to confound and mislead would-be attackers. These false entrances, cleverly constructed, often led invaders to dead ends or traps, granting a tactical advantage to the defenders. A fortress’s deceptive entrance could be a disguised gate or a concealed passage purposefully designed to confuse and frustrate enemies. These strategic illusions created a sense of mystery and uncertainty, leaving attackers vulnerable and susceptible to counterattacks. The element of surprise was a powerful weapon employed by the defenders of ancient medieval fortresses, heightening the enigmatic aura surrounding these formidable strongholds.

The ingenious design of false entrances exemplifies the resourcefulness and ingenuity of ancient castle builders. These deceptions played a significant role in castle defense, serving as a means to outwit and thwart potential invaders. By leading attackers astray or luring them into traps, these false entrances provided defenders with a crucial advantage, enabling them to control the battlefield and safeguard the fortress. The secrets hidden within these false entrances contribute to the mysterious allure of ancient medieval fortresses, reminding us of the creative tactics employed to protect these monumental structures throughout history.^[3]

7 Acoustic Warfare

Within the ancient medieval fortresses, a mysterious form of warfare unfolded through strategic architectural designs aimed at manipulating sound. These fortresses employed specific shaping of walls, chambers, and tunnels to create echoing effects, disrupting communication and coordination among potential intruders. The deliberate use of acoustics added an enigmatic element to these strongholds, impeding the effectiveness of attackers and enhancing the defenders’ advantage. The echoes bouncing off the walls created a disorienting atmosphere, shrouding the fortress in an eerie ambiance and leaving invaders unsure of their surroundings.

The utilization of acoustic warfare in ancient medieval fortresses showcases the innovative strategies employed in defensive architecture. By harnessing the power of sound, these fortifications could sow confusion and hinder the progress of assailants. The deliberate shaping of certain structures to amplify and distort sound added an intriguing dimension to the secrets of these ancient strongholds.

The mastery of acoustic warfare allowed defenders to exploit the natural environment to their advantage, further enhancing the mystique surrounding these fascinating medieval fortresses.^[4]

6 Trapdoors and Trickery

Ancient medieval fortresses harbored a multitude of secrets, employing ingenious trapdoors and deceptive mechanisms to outsmart invaders. These hidden tricks played a crucial role in safeguarding the fortress and catching intruders off guard. False floors, disguised entrances, and concealed pitfalls were just a few of the tactics used to confound and confuse potential assailants, ensuring the defenders held the upper hand. These secret mechanisms were designed with great precision, reflecting the castle inhabitants’ resourcefulness and their determination to protect their stronghold.

The implementation of trapdoors and trickery in ancient medieval fortresses demonstrates the strategic brilliance of their architects. These hidden devices and concealed traps created an aura of mystery and danger within the fortress walls, deterring intruders and thwarting their progress. The secrets held within these fortresses showcased the cunning and innovation employed by the defenders, adding an air of mystery and intrigue to these formidable structures.

Exploring the secrets of trapdoors and deceptive mechanisms provides a glimpse into the ingenious tactics used in ancient medieval warfare, revealing the lengths that castle inhabitants went to ensure the safety and security of their stronghold.^[5]

5 Secret Rooms and Chambers

Behind the formidable walls of ancient medieval fortresses, secrets lay hidden within secret rooms and chambers. These concealed spaces provided sanctuary for important individuals or safeguarded precious valuables shrouded in the fortress’s secretive past. These hidden compartments served various purposes, serving as clandestine meeting places or concealed storage spaces. Exploring these covert rooms unveils the intriguing history and mysteries that surround these ancient fortresses.

Medieval castles were not merely fortifications but also centers of intrigue, and secret rooms and chambers were an integral part of their architecture. These hidden spaces played a crucial role in defense, escape, and the preservation of valuable possessions. From the Queen’s Chamber in the Tower of London to the Secret Room at Château de Brissac, these hidden compartments continue to captivate our imagination, revealing the secrets and stories of the past.

The discovery of these covert rooms within ancient medieval fortresses sheds light on the intricate design and fascinating history that lies beneath the surface, reminding us of the hidden wonders that await within these architectural marvels.^[6]

4 Whispering Galleries

Whispering galleries—mysterious architectural features found within ancient medieval fortresses—continue to intrigue historians and visitors alike. These curved passageways or chambers possess a unique acoustic property, allowing whispers to travel astonishingly clear across long distances. The purpose behind these whispering galleries remains shrouded in mystery, leaving us to speculate on their significance.

Legends and stories surrounding whispering galleries evoke images of clandestine conversations, secretive exchanges of information, and hidden romance. Places like the Loggia dei Mercanti beneath Milan’s Palazzo della Ragione and the Whispering Gallery at St Paul’s Cathedral in London offer immersive experiences where whispers are carried effortlessly through the air, inviting us to indulge in the intrigue and enigma they hold.

Whispering galleries are not limited to medieval fortresses alone; they can be found in various locations around the world. From the Gol Gumbaz Mausoleum in Vijayapura to the Grand Central Terminal in New York, these curved architectural wonders provide captivating acoustic experiences. St. Paul’s Cathedral in London features a renowned whispering gallery within Christopher Wren’s grand dome, where whispers can be heard clearly across the circular walkway.

Other notable whispering galleries include the Lovers Bench in Spain, the Echo Wall at the Temple of Heaven in Beijing, and the Whispering Arch in Görlitz, Germany. These remarkable structures continue to amaze and captivate visitors, offering a glimpse into the marvels of architectural design and the mysteries of sound [8][9]. ^[7]

3 Treacherous Staircases

Treacherous staircases were cleverly incorporated into some ancient medieval fortresses to impede and confuse potential attackers. These staircases were intentionally designed with uneven steps, hidden sections, or changing directions, creating obstacles that could trip up and slow down invaders. The treacherous nature of these staircases added an element of mystery and danger to the fortress, making it challenging for assailants to navigate the stronghold and reach their intended targets. The strategic placement of these deceptive staircases showcased the ingenuity of medieval fortress design, leaving attackers vulnerable and giving defenders an advantage in repelling sieges.

It is worth noting that there is a misconception surrounding medieval spiral staircases, particularly the belief that they were designed clockwise to favor right-handed defenders in combat. However, this notion lacks historical evidence and is not supported by primary medieval sources. The primary focus of fortress defense was to prevent attackers from entering, making staircase design less relevant for fighting purposes.

The actual purpose of the clockwise design was likely rooted in everyday safety and practicality, allowing right-handed individuals to maintain balance while descending. Nonetheless, the presence of treacherous staircases in ancient medieval fortresses remains a captivating aspect of their architecture, adding to the enigmatic aura that surrounds these historic structures.^[8]

2 Concealed Armories

Medieval fortresses held their share of secrets, and one of the most intriguing was the concealed armory. These hidden weapon caches were cleverly tucked away within the fortress, concealed within walls, floors, or secret compartments. The purpose of these concealed armories was to ensure that defenders could arm themselves swiftly during a siege, catching their foes by surprise. The hidden caches allowed defenders to access weapons and supplies without revealing their location, adding an element of mystery to the fortress’s defense strategy. It highlights the importance of surprise and preparedness in protecting these formidable structures.

Fortresses employed various tactics to safeguard their concealed armories. Secret compartments within walls or floors provided discreet storage for weapons, shields, and ammunition, keeping them hidden from view. These hidden weapon caches allowed defenders to arm themselves quickly, even when the castle was under attack. By keeping the location of the armory a secret, fortresses enhanced their defense capabilities and increased the element of surprise during a siege. The concealed armories were an essential part of the fortress’s overall strategy, ensuring that defenders had immediate access to weapons when they needed them most, catching their foes off guard and potentially turning the tide of battle.^[9]

1 Inaccessible Towers

Within the ancient medieval fortresses of yore, a veil of mystery surrounds the enigmatic inaccessible towers. These towers, intentionally built without staircases or entrances, remain shrouded in secrets. Their purpose, lost to the annals of time, sparks curiosity and speculation. It is believed that these isolated towers served as vantage points, providing an unparalleled view of the surroundings or as the final bastions of defense during times of siege. The absence of staircases or accessible entrances only deepens the intrigue surrounding these towers, leaving behind a lingering aura of mystery that adds to the mystique of fortress design.

In the realm of ancient medieval fortresses, inaccessible towers stand as silent sentinels, guarding their secrets with steadfast resolve. Perched high above the fortifications, these tower enigmas tantalize the imagination and hint at their hidden purpose. Whether they served as watchtowers or held crucial defensive functions, the true intentions of these towers remain veiled, lost to the passage of time.

Their isolation adds an air of intrigue, stirring the imagination and inviting exploration into the enigmatic world of ancient medieval fortresses. These inaccessible towers continue to stand as silent witnesses, beckoning adventurers to uncover their secrets and unravel the mysteries that lie within the heart of these ancient fortresses.^[10]