One of Europe's most mysterious landmarks, the bewitching Quinta da Regaleira in Sintra, Portugal was built by an eccentric tycoon with a penchant for the occult. Inspired by alchemy, the Knights Templar, Freemasonry and more, the castle is peppered with esoteric symbols and curious design enigmas. But the estate's subterranean secret concealed some 88 feet below the ground is its strangest and most mysterious feature...

Click or scroll through to explore the magnificent estate inspired by the occult and decode its many puzzles.

Quinta da Regaleira is one of the jewels of Sintra, an affluent locale just outside Lisbon. Nestled in the foothills of the evocatively nicknamed Mountain of the Moon, the town served as a country retreat for Portugal's royal family and other members of the country's high society for hundreds of years.

The beguiling 10-acre estate takes pride of place on one of Sintra's most prominent hills and benefits from UNESCO World Heritage Site status.

Pictured here are the ornate main gates of Quinta da Regaleira. The sprawling estate references a whole host of architectural styles, from Renaissance and Ancient Roman to Gothic and Portuguese Manueline.

The estate was the brainchild of eccentric tycoon António Augusto Carvalho Monteiro. Born in Brazil and raised in Portugal, he inherited the family fortune and earned the moniker 'Monteiro the Millionaire'. 

The land the estate lies on belonged to the Viscountess of Regaleira, a family of affluent merchants from Porto, before it was sold in 1893 to Carvalho Monteiro.

Obsessed with alchemy, Freemasonry, the Knights Templar and Rosicrucianism – a spiritual and cultural movement that emerged in early modern Europe – Carvalho Monteiro set about creating an enchanting, mystical estate that reflected his avid interests.

Pictured here is the stairway leading up to the Quinta da Regaleira Palace.

Monteiro turned to flamboyant Italian-born set designer and architect Luigi Manini to make his whimsical vision for the estate a reality. Manini had purportedly impressed Carvalho Monteiro with his work on Buçaco Palace, a masterpiece in the exuberant neo-Manueline style, which combined Renaissance and Gothic aesthetics. With money seemingly no object, Manini could let his imagination run riot. Construction began in 1904 and the estate was completed by 1910.

While some of his interests could be described as radical and unorthodox, Carvalho Monteiro was a staunch monarchist and traditionalist who wanted to honour Portugal's Golden Age. The neo-Manueline style, which exemplifies the country's 16th-century heyday, was the go-to architectural style for his home. The Quinta da Regaleira Palace is considered one of the finest examples of neo-Manueline in Portugal in the 19th and 20th centuries.

The principal entrance showcases the palace's exquisite limestone decoration. The spectacular space features myriad carvings of human figures, animals, nautical elements and other Manueline symbols. No doubt hours of work went into its elaborate execution. 

The palace is no less impressive inside. So named for its lavish Italian Renaissance-style décor, this palatial space served as the formal living room.

With its spectacular coffered oak ceiling, meticulously carved timber wall panels and sumptuous marble detailing, the Renaissance Room references the grand palazzos of Florence and Siena. Note the gilded icons that stud the wall at regular intervals – monograms that represent the union of Carvalho Monteiro with his beloved wife Perpétua Augusta.

The highlight of the palace's Hunting Room is this regal fireplace. Created by sculptor Rodrigo de Castro, the marble masterpiece portrays various hunting scenes and is topped by a figurine of a proud huntsman.

Symbolism abounds throughout the room. The hearth alludes to part of its former owner's surname, as Monteiro means hunter in Portuguese. Meanwhile, the wide use of oak and the numerous depictions of the tree are nods to his other surname Carvalho, the Portuguese word for oak. As described by academic Paulo Pereira, this "speaking heraldry" pervades the estate and is a testament to Carvalho Monteiro's preoccupation with allegory.

Carvalho Monteiro's reverence for Portugal's monarchy comes to the fore in the King's Room, which was formerly the billiards room. It's named on account of the 24 portraits of the country's monarchs that encircle the top of the walls in a decorative frieze, alongside the coats of arms of Portuguese cities, including Braga, Porto, Coimbra and Lisbon.

The palace has six floors but only two are open to the public. The two basement floors house kitchens, larders, a scullery, an ironing room and a staff dormitory.

Other key spaces include the library. Carvalho Monteiro had a passion for books and his collection of 30,000 tomes, which included rare works by Portugal's venerated 16th-century poet Luís de Camões, was later sold to the US Library of Congress. Among the largest purchases in its history, the collection formed the backbone of the library's Hispanic Division.

Elsewhere in the palace, this magnificent formal room is lined with a series of framed painted murals depicting high-society courting scenes. An ornately carved surround crowns the door, while polished Versailles parquet lines the floors. 

Unsurprisingly, the extravagant palace requires a regular schedule of upkeep. In April 2024, preservation work took place across the interior to ensure its elaborate spaces can be enjoyed for years to come. 

The palace's soaring octagonal tower is among its extraordinary architectural features and provides breathtaking views of Sintra, the surrounding countryside and beyond.

On top of the tower is something of an eccentric menagerie – the roof terrace is adorned with statues of animals, including a rabbit, rooster, kangaroo and some fantastical hybrid beasts. They are said to reflect Carvalho Monteiro's love of nature, but local legend suggests the mythical hybrids may also symbolise his interest in transmutability and alchemy.

Mythical hybrid animals also decorate the Renaissance House, which is just north of the palace. They feature on the building's Terrace of the Chimera, which has a fountain supported by five chimeras, each made up of a lion's head, a goat's body and a dragon's tail.

It's thought that the property was once the home of the estate's caretaker. These days it's the headquarters of the Cultursintra Foundation, a public organisation that promotes cultural endeavours throughout Sintra. 

Across from the Renaissance House is the Quinta da Regaleira Chapel, one of the most intriguing buildings on the estate. Like the palace, the chapel is designed in the neo-Manueline style, featuring highly ornamented mouldings, a spectacular tower and spires. 

While it may initially resemble a Catholic place of prayer, on closer examination, it draws from a whole host of spiritual and esoteric influences...

Inside, the floor is decorated with a Templar cross surrounded by pentagrams and pagan sunwheels. A Templar cross also features in the entranceway, along with other esoteric symbols including the Rosicrucian rose and the Holy Grail chalice.

A painting of the Virgin Mary being crowned by Jesus presides over the altar. However, if you look closely at the arch above the icon you can glimpse a letter M carved into the moulding. Its meaning is up for debate – it could signify the Madonna, Monteiro or perhaps even Freemasonry. 

A glance at the elaborate ceiling reveals another potent Masonic symbol, the All-Seeing Eye or the Eye of Providence. It symbolises God as the Great Architect of the Universe observing every deed, according to Freemason mythology. In Masonic halls and lodges, the eye is often depicted within a triangle with rays of light seemingly emanating from it, as is the case here. 

The Masonic references continue in the church's crypt, which features black-and-white checkerboard floors. This patterned flooring is commonly found in Masonic lodges and symbolises light and dark or the moral fallibility of humankind. Other emblems found throughout the church include symbols associated with the Order of Christ, the successor to the Templar Order in Portugal. 

Allowing the estate's residents to navigate the acreage unseen, the crypt also contains a secret subterranean passage that connects the space to the main palace.

This folly and fountain along from the chapel pay homage to the sacred ibis. The bird was revered by the Ancient Egyptians as the carrier of souls to the afterlife. The Ibis is also linked to Thoth, the Ancient Egyptian god of the Moon, learning, writing, wisdom and magic.

The estate's grounds are reportedly structured as a mythological journey of sorts, guiding visitors through the symbolic gardens as though on a quest akin to those faced by the heroes of famous Greek epics such as The Odyssey and The Iliad. 

Nearby, the stunning Fountain of Abundance is bursting with Masonic symbolism. It features a pair of obelisks that represent Joachim and Boaz, the two pillars of the secret society that are commonly found in Freemason architecture.

Carvalho Monteiro's initials grace the centre in an elaborate mosaic. Local legend speculates that the M could also be a reference to Freemasonry.

On top of his penchant for all things esoteric, Carvalho Monteiro was a passionate naturalist. A member of almost every natural history society of the time, he discovered a considerable number of insects and plants and even helped to found Lisbon Zoo.

Some of his vast collection of flora and fauna were no doubt housed in this stone-walled greenhouse. Carvalho Monteiro's love of nature is also evident in the grounds, which are wonderfully lush and replete with plants carefully chosen for their mystical associations, including yew, oak and cypress trees. 

The Waterfall Lake is situated in the middle of the estate. A blissful idyll, the lake is traversed by a bridge that looks like it was hewn out of natural rock.

Following a fall, Carvalho Monteiro died on 24 October 1920, around a decade after the completion of his mystical sanctuary. He was 71 years old.

The estate was eventually sold in 1942 to sculptor Waldemar d'Orey. Then in 1987, Quinta da Regaleira was snapped up by Japan's Aoki Corporation, which for reasons unknown, kept it shuttered. The estate was finally acquired by the local town council a decade later and opened to the public in 1998, the same year it became a UNESCO World Heritage Site.

The Ziggurat is situated in the middle of the estate and is one of two towers that punctuate an area known as the Terrace of the Celestial Worlds. The seven-storey lookout folly was inspired by the pyramid-like ziggurats of Ancient Mesopotamia.

Whether Carvalho Monteiro was an active Freemason is a matter of debate. Some sources claim he had no documented connection to the secret society, while others say he was a fervent member. Academic Paulo Pereira thinks it's likely he knew Freemasonry and other "esoteric circles" reasonably well. 

Indeed, it's clear from the design of the estate that Carvalho Monteiro possessed a lot of knowledge about the intricacies of Freemasonry, the Knights Templar and Rosicrucianism, and went to much trouble to imbue his estate with mystical symbolism.

On the other side of the Terrace of the Celestial Worlds stands the imposing Portal of the Guardians. This monumental fountain is guarded by two mythical creatures. But what are they guarding? As you can see, there are several doors that lead inside the structure...

The Portal of the Guardians is one of the entrances to the estate's most perplexing feature. Inside, a tunnel leads from the fountain to the astonishing Initiation Well.

Descending 88 feet underground, the inverted tower never served as a water source. While the exact purpose of the well can't be known for sure, it's riddled with symbols of the Knights Templar, leading many to believe it was used for initiation ceremonies.

The Catholic military order is thought to have disbanded over 700 years ago, however, the rituals of the Knights Templar were adopted in part by the Freemasons centuries later. Let's take a look...

The well consists of nine levels lined with ionic columns, said to represent the nine founders of the Knight's Templar or the nine circles of heaven, purgatory and hell in Dante's Divine Comedy. 

If the structure was indeed used to initiate new members of the secret society, the blindfolded candidate would have entered the covered walkway at the highest part of the well and descended the nine flights that make up the spiral staircase, clutching a sword close to their heart, according to the BBC. 

There are 139 steps in total. Again, the number isn't random and is said to have been carefully chosen by the well's architects. One, three and nine added together equal 13, a sacred number in numerology that's said to represent death and rebirth, as well as signifying a move to a higher state of consciousness.

At the bottom of the well is a Templar cross and an eight-pointed compass rose inlaid stone, which could be a reference to Rosicrucianism or Freemasonry. 

Looking up from the bottom of the well is a surreal experience. Apart from the awe-inspiring architecture, what strikes many visitors is how the view from the bottom is strikingly similar to the one from the top.

Built at the same time as the palace, the well must have cost a pretty penny to construct, not to mention the amount of time it must have taken to excavate 88 feet below ground. 

Once the initiation ceremony in the well was completed, the blindfolded candidate, who was yet to be brought into the fold at this point, had to enter a pitch-black labyrinth. In a literal and metaphorical quest toward the light, the ritual participant had to find their way out of the maze of tunnels. Each passage leads to different exits including the Portal of the Guardians, but the luckiest candidates would have emerged into daylight at the Labyrinthine Grotto, part of the Waterfall Lake.

Upon reaching the water, the next challenge was to cross the lake via the stepping stones. If the aspiring initiate was able to pull it off, they would make their way to the chapel where they would reportedly be welcomed into the brotherhood. The symbolic journey to enlightenment was complete.

Of course, this could all be wild speculation. But the existence of another initiation well on the estate would seem to support the theory. It's unlikely Carvalho Monteiro would have commissioned a second well had he not needed the bizarre amenity for a specific purpose.

Dubbed the Unfinished Well, it languishes in an incomplete state and is shallower than its sibling at 33 feet deep. Whereas the original Initiation Well is orderly in its design, with elegant arches and columns that are perfectly proportioned, the Unfinished Well is rough and unhewn.

Among the labyrinth of tunnels that connect to the main Initiation Well, one particular tunnel leads to the Unfinished Well, suggesting the two vertical towers were intended to have a connected purpose. 

It's not clear why the second well was never completed – another mystery to add to the list. Perhaps it was intentionally left unfinished or maybe something forced construction to abruptly stop. Like Quinta da Regaleira's other enigmas, we'll probably never find out.

An eccentric with a fantastical imagination, Carvalho Monteiro left behind an architectural triumph and a breathtaking monument to his love of the occult that will continue to delight visitors for years to come. 

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