Revered for their exquisite architecture, storied pasts and notable former residents, not everything is as it seems in these regal stately homes. From concealed rooms to escape tunnels, disguised doors and priest holes, there's a warren of secret spaces hiding within their historic walls. Let's uncover some of the most fascinating clandestine features in the grandest palaces and castles around the globe...

Looming out of the cliffs, the world’s largest cave castle in Slovenia appears have grown out of the rock itself. Standing 115 feet above ground level, this medieval marvel dates back to the 13th century and proved to be the perfect hideout for a robber baron. Erasmus of Lueg, a 15th-century knight, fell foul of the Habsburg rulers of the region and took refuge in the rocky fortress.

Now an outlaw, he lived up to his reputation by raiding Habsburg towns. Legend has it that his enemies tried to stave Erasmus to death by laying siege to the castle for around a year. With no apparent way in or out, the attackers expected the knight and his people to surrender, but they didn't. In fact a secret supply passage, pictured here, kept the occupants of the incredible cave home fed and watered!

The rebel knight was using the castle’s spider web of secret tunnels, linked to a main supply passage, to come and go freely. While the invaders sweated it out below the fortress, Erasmus got plentiful food and wine from a nearby village. It’s said that he pelted the puzzled invaders with fresh cherries to prove how much food he had! The siege ended when Erasmus was reportedly betrayed and assassinated. The secret passage is preserved for 21st-century visitors to retrace the steps of the roguish robber baron.

Dating back to the 1300s, Harvington Hall is a stunning moated medieval manor that’s riddled with secrets. Additions to the building were made in the late 1500s and early 1600s by the devoutly Catholic Pakington family during the Protestant Reformation – a time when following the denomination could spell death if the authorities discovered you. Patriarch Humphrey Pakington commissioned a series of cleverly concealed spaces where the ministers of his faith could hide should the queen’s men come calling.

Determined to practice his religion and protect the home's priests, Pakington had many hides installed around the house – historic panic rooms of sorts. Four of them, situated around the great staircase, were built by Jesuit lay brother Nicholas Owen. Here, you can see the kitchen hide, which was built in around 1612. While it looks dank and uncomfortable, it was a much better alternative than the punishment for treason!

Part of a network of safe houses for Catholic priests, this diagram of the hides shows just how numerous they are. Notice how a false fireplace in the marble room leads to two hides in the attic. Architect Nicholas Owen was seized from one of his own hides by government troops in 1606 and was cruelly executed at the Tower of London.

The ancient hilltop town of Civita di Bagnoregio in central Italy was first settled by the Etruscan civilisation over 2,500 years ago. A breathtakingly scenic spot, the medieval settlement sits on a huge promontory of volcanic rock in the middle of a vast valley. 

Nestled in the commune, Domus Civita is a captivating 14th-century palazzo, renovated in 2011 by architect Patrizio Fradiani of Studio F. The three-bedroom property has a formal Italian garden, an outdoor kitchen, a gazebo and a wine cellar. It also has secret subterranean caves, connected to the house by underground passageways – this one offers the blissful luxury of a heated pool and hot tub.

Winding your way through the warren of tunnels, you’ll find this tranquil cavern, perfect for relaxation. Lit by soothing lamps and candles, it's decked out with soft floor cushions so you can kick back and soak up the ambiance. Best of all, it’s available to rent via Airbnb.

This Gothic Revival-style mansion in the centre of Toronto was built in 1914 for a wealthy banker. Perched on Davenport Hill, 459 feet above sea level, Casa Loma is Spanish for ‘hill house’. Turned into a hotel during the 1920s, it became a popular hotpot for American socialites during Prohibition. Its eye-catching architecture means the famous movie home has been a location for blockbusters including X-Men, Chicago and Crimson Peak.

With 98 rooms, 30 bathrooms and 25 fireplaces, it’s not too surprising that there are a couple of hidden tunnels thrown in for good measure. Indeed, it has several secret passages and staircases, including this 800-foot tunnel connecting the mansion to the estate's grand stables – the perfect equestrian property for an undercover spy!

Fitted with smart herringbone tiled floors, mahogany walls and cast-iron panels, there's more to these gilded stables than meets the eye. Amazingly, they were once a secret room for developing classified military technology. During the Second World War, cutting-edge anti-submarine sonar sensors were produced here. Anyone attempting to enter was reportedly deterred only by a small padlock and a sign reading: ‘Construction in progress. Sorry for the inconvenience’. Little did most people know that military secrets lay inside!

This island castle stands on a limestone rock on the banks of Lake Geneva, with the snowy Chablais Alps as a picturesque backdrop. Dating back to the 10th century, this historic house passed through the hands of numerous Swiss aristocratic dynasties. With attractive Romanesque architecture and layers of history, it’s easy to see why it attracts 400,000 visitors per year. You’ll find several secret passageways inside connecting the bedrooms, but it’s beneath the building where the big surprise lurks.

Usually dank and dingy, dungeons are not normally known for their elegant designs. Although it’s definitely dark, this dungeon is surprisingly architecturally pleasing, with its soaring Gothic vaults which would look more at home in a cathedral than a prison. Although you might not feel like admiring the architecture if you were chained to one of those pillars, which leads us on to another fascinating secret…

English Romantic poet Lord Byron visited the castle in 1816 and was so taken with its mysterious dungeon that he wrote a poem about it. The Prisoner of Chillon describes the plight of real-life political prisoner François Bonivard, who was supposedly shackled to the dungeon’s pillars. Byron's name is carved in the dungeon, but the authenticity of the signature is hotly debated. 

Coughton Court is a Tudor country house with a turbulent history. The long-time home of the Throckmorton family since 1409, patriarch John de Throckmorton was the Under-Treasurer of England to King Henry VI, however, the estate's fortunes took a turn for the worse during the 16th-century English Reformation, which resulted in the religious persecution of Catholics. It was this oppression that gave rise to the need for a secret space inside this enchanting stately home.

This opulent bedroom, with its four-poster bed, wall-hung embroideries and centuries-old oil paintings, conceals a potentially life-saving hidden room. That’s because the Throckmortons were Catholic – and the price for practicing the banned faith at this time was a one-way trip to the Tower of London. So, the family created a clandestine nook to hide their outlawed priest.

This odd-looking secret space is actually a priest hole. It's very well concealed and contains a rope ladder, a small tapestry, bedding and a folding leather altar. This tiny time-capsule room had been hidden away for centuries and was only rediscovered in 1910.

Perched on the pink sandstone peaks of the Vosges Mountains, Mont Sainte-Odile Abbey has been a place of scholarly reflection for more than a thousand years. Now a hotel and spiritual retreat, the mysterious monastery has been pretty unlucky over the centuries, having been struck by lightning and decimated by fires several times. A center of mysticism, encircling the building is the enigmatic Pagan Wall, thought to have been built by the Celts, however, the abbey's most intriguing feature lies inside...

The abbey’s library is full of centuries-old, priceless manuscripts. But between August 2000 and May 2002, hundreds of these ancient books went missing from its shelves. Detectives were baffled by the thefts, as the library showed no signs of a break-in. Locks were changed and doors reinforced, but still more books were stolen. Eventually, the puzzling case was unravelled in quite an accidental way...

The mystery was solved when a police officer pushed the back of one of the library's bookshelves, revealing a small secret room and a rope ladder that eventually led to the convent's workshop. With the authorities lying in wait, the thief – a mechanical engineering teacher with a penchant for Latin – was caught. He'd found a lost map, reportedly pictured here, in the public archives that showed the forgotten space. Having stolen the books because of his passion for the ancient artefacts, they were all safely returned.

A brooding fortress with a dark past, Bran Castle is set high on a hill in Transylvania. The pretty tiled turrets and towering white walls give it a fairytale feel, but its history is altogether more nightmarish. The site of gory battles across the centuries and the rumoured prison of Vlad the Impaler, the castle has certainly seen its fair share of turmoil. Some think the fortress may have been the inspiration for Count Dracula's castle in the famous horror novel by Bram Stoker.

As the centuries ticked by, the castle left its blood-stained history behind as it became the refined residence of Queen Marie of Romania. Born into the British royal family, Marie was a granddaughter of Queen Victoria. In 1920, Bran Castle became her royal retreat and she set about renovating the medieval estate. While turning this room into a fashionable salon, a secret staircase was discovered.

It’s thought to have been used as an escape passage, connecting the first floor to the third. Hidden inside the wall, the tunnel allowed the castle's residents to flee from danger and elude any pursuers. A fake fireplace concealed the entrance to the passageway so convincingly that it was forgotten for decades. Now the staircase is not so secret as it’s on display for visitors to see.

Built around 1482, Oxburgh Hall is a moated stately home with an imposing fortified gatehouse, complete with tall towers. Victorian architectural additions include Flemish-style gables, protruding oriel windows and terracotta chimneys. Amongst the ornate design details, there's also a couple of intriguing secret spaces hiding in plain sight...

Like some of the other grand homes in our roundup, the property has a concealed priest hide, reached by a trapdoor inside one of the turrets. It cleverly blends in with the tiled flooring when closed, neatly disguising the entrance. Pictured here is the library, which is home to a more creative concealed feature...

One of the bookcases is in fact a hidden door. The attention to detail is startling – the spines of the fake books, which are painted over the disguised door, contain titles that jokingly refer to events and people from Oxburgh's history. There's dedication to deception for you! You'll find six other secret doors hidden around the mansion – perfect for a game of hide and seek.

An Elizabethan mansion with classical Renaissance architecture and a somewhat quirky secret, Montacute House is constructed in an E-shape, which is typical of the period, with curving Dutch gables decorated with stone monkeys. It has links to the Gunpowder Plot of 1605, as one of its owners led the prosecution's opening argument in the trial of Guy Fawkes. 

In 1915, Elinor Glyn, a novelist deemed scandalous for the time, also moved into the house for 18 months with her lover, Lord George Curzon. A keen interior decorator, she set about transforming the cold, musty interior of the old house. She decked the place out with fine fabrics, fur rugs and ornaments from luxury department store Liberty London. But it was in the bedroom that this risqué writer added a secret compartment…

For a witty touch, she installed a bright red roll-top, claw-foot bath in the bedroom, surrounded by beautiful red bathroom tiles – quite an eccentric addition. Even more intriguingly, it's tucked away behind panelled wooden doors, perhaps to prevent steam dampening the room. 

Set amid scenic natural beauty, Admont Abbey is located on the tranquil Enns River next to the mountainous Gesäuse National Park. Although founded in the 11th century, some parts of the structure only date back to the 19th century, after a fire damaged swathes of the original building in the mid-1800s. However, one secret feature hidden within its walls has stood the test of time...

Luckily, the abbey's magnificent library survived the fire. Completed in 1773 in the theatrical Rococo style, it's the largest monastic library in the world, holding about 70,000 books – and it really is a feast for the eyes! Covered in gloriously detailed frescoes that depict divine wisdom and revelation, huge windows illuminate the space, making the golden gilding on the walls sparkle.

In a room where the eye is dazzled by the décor, it’s fitting that there are a couple of tricky secrets to unravel. Almost indiscernible, disguised doors have been cleverly built into the bookshelves. Painstakingly painted with faux book spines, the mysterious exits conceal four spiral staircases leading up to the library gallery.

The beginnings on this moated manor were built in the 15th century by John Brome on the site of an old farmstead, with the architectural proportions of the house set by the shape of the older moat surrounding it. Impressive stained-glass windows depicting a later family’s coat of arms were installed in the late 16th century and some still survive today, as do a number of curious hidden rooms.

Here, you can see the house’s ornate interior, filled with plush fabrics, carved wooden furniture and decorative tapestries. Scandal hit the house in the late 1400s when Nicholas Brome, the son of John Brome, murdered the estate's priest in the parlour, reportedly after catching his wife in a compromising position with the clergyman. Despite this bloody episode, the house would later prove to be a place of sanctuary for priests.

Over a century later around 1590, a concealed network of priest holes in Baddesley Clinton were used to hide priests during the Reformation. Reached through a secret passageway, one priest hole is located off the moat room, via a door hidden in the wooden panelling. A second tunnel leads to a chamber in the ceiling, while a third room is hidden in the distinctly unappealing location of an old lavatory – to reach it, it's said fugitives had to slide down a rope through the toilet opening into the sewer. Not exactly luxury accommodation!

Rising out of woodland, the dramatic Gothic-style exterior of this Portuguese palace conceals many secrets. Completed in 1910 for a noble family, it was later bought by a businessman, nicknamed Moneybags Monteiro. He set about commissioning surreal sculptures and occult symbols to reflect his interest in esoteric beliefs. You’ll find covert references to Freemasonry, the Knights Templar and pagan gods carved into the house and gardens. But its biggest architectural mystery lies beneath your feet...

Spiralling deep into the earth, the palace’s two initiation wells must rank among the most mind-blowing architectural finds on the planet. You can walk inside the twisting underground towers, plunging 88 feet down into the ground, to eventually reach a tiled floor decorated with Knights Templar symbols. It's said to feel eerily quiet and cold inside the well – very much as if you’re stepping into a mystical realm. The hidden wells are rumoured to have been where people were initiated into secret societies. 

Leading out from the initiation wells are a network of dark and mysterious passageways, hewn from the rocky landscape. Although these magical tunnels seem as if they were natural occurrences, in fact, they are entirely man-made – all part of a labyrinthine architectural plan, just waiting to be explored. Secret spaces don't get much more spectacular than that!