You may have visited some of the world's most famous attractions, but did you discover some of their deepest secrets? From hidden chambers, secret tunnels, ancient rituals and covert apartments, there are many mysteries waiting to be uncovered in well-known landmarks. Here we reveal some of them…

Once you’ve explored the galleries and dodged the people and pigeons, take a stroll down to the southeast corner of Trafalgar Square to see if you can spot one of London’s many oddities – the city’s smallest police station...

Built into a lamp post, it was installed in 1926 to allow a policeman to keep watch on demonstrators at the popular protest site with a direct line to Scotland Yard. Today, its use is rather more mundane – it’s used as a storeroom for cleaners.

Mount Rushmore is one of the US’ best-known attractions, drawing more than three million people every year. But many don’t realise that a hidden corridor lies behind the gigantic granite head of President Abraham Lincoln...

It was meant to be part of a Hall of Records, envisioned by the monument's sculptor, Gutzon Borglum, to store important documents about America’s history, but it was never completed. It was only in 1998 that the National Park Service added a titanium cask with 16 porcelain panels about Mount Rushmore's history.

The most famous Roman monument of all, the Colosseum draws visitors by the millions. But few duck down to the hypogeum, a system of underground tunnels that open up a whole new perspective of the vast amphitheatre.

The subterranean space was used to keep gladiators and exotic animals (including elephants, leopards, panthers and bears) before they were lifted up to the main arena by a system of winches and pulleys to do battle. Closed to the general public until several years ago, tours of the hypogeum are now possible.

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The first railway station to be built in an Australian city, Melbourne’s Flinders Street Station is one of the city’s most beloved buildings. The terminal has appeared in a number of movies too, but visitors rushing to catch their trains will not notice one of the most fascinating elements of the train station: its secret abandoned ballroom.

On the third floor of the building, the ballroom once held concerts, competitions and public dances. However, it has been empty ever since the 1980s and is now in a state of disrepair.

Located on top of the hill al-Sabika, on the left bank of the river Darro, there’s plenty to keep you intrigued above ground at Granada’s imposing Alhambra. However, even more intrigue lies hidden below the majestic palace...

A mysterious underground tunnel complex lurks beneath the grand hilltop Moorish palace. The passageways connect the Alhambra with Albaicín, the town’s old Arabic neighbourhood, and were most likely used for storage, to transport provisions in and allow people to come and go unseen during times of siege.

Erected at the end of London Bridge in 1677 to celebrate the rebuilding of the city after the Great Fire of London, the Monument is 202-foot-high, the exact distance between it and the site where the fire began on Pudding Lane. Hundreds of thousands of visitors have climbed its steps over the years to enjoy views over England's capital, but it isn't just a monument...

More than a clever landmark, the Monument was built as a giant telescope and planned to be used as the site of scientific experiments. Off limits to the public, a tiny laboratory sits underneath the building.

It has been in countless movies, offers exceptional views across New York City and was once the tallest building in the world. The Empire State Building plays host to millions of visitors every year, but most are unaware of the tower's big secret...

The observation deck on the 103rd floor of the Empire State Building is closed to the public, but celebrities such as David Beckham as well as movie makers are whisked through a secret door and up some narrow steps to gain access to the railing-free viewing level. The rest of us will have to be satisfied with the views from the building’s 86th and 102nd floor observatories.

Another famous tower with a lofty secret space is the Eiffel Tower. Gustave Eiffel built himself a pied à terre on the third level of the tower for work and to entertain the occasional esteemed visitor such as Thomas Edison. Eiffel used the small apartment to make astronomical and physiological observations.

Today, visitors can peek in the office, which has been restored to its original condition complete with wax figures of the engineer and pals, wooden furniture, oil paintings and patterned wallpaper. The apartment was reportedly in demand in Parisian high society in the 19th century, with several people offering Eiffel large sums of money to rent the space even for one night, but never succeeding.

One of the largest train stations in Europe, Milan’s elegant Stazione Centrale hides an intriguing secret space with a dark past...

Within the station keep an eye out for the entrance to the Padiglione Reale (Royal Pavilion), a luxurious two-level waiting room, near platform 21. It was built in the 1920s for the Italian royal family, the Savoias, as they waited to board a train to their countryside palace. Swastikas were added to wood flooring in its main room in anticipation of hosting Hitler, although he never used it. Today the pavilion is used for special events and occasionally opened for public tours.

An iconic sight among London's skyline, Sir Christopher Wren’s cavernous St Paul’s Cathedral has plenty of hidden nooks and crannies. One rarely seen but stunning part lies in the southwest tower – the Geometrical Staircase which links the cathedral floor to the triforium.

Movie buffs will recognise it as the route to the Divination Classroom in Harry Potter and the Prisoner of Azkaban. You can join a guided tour to see the spectacular stone spiral, the Chapel of St Michael & St George, Wren’s Great Model and the Quire, areas not normally accessible to the public. Although, the library is closed until summer 2020 for a major conservation project. 

One of the most famous addresses in America sparks intrigue at the best of times, and if you watch a few political US dramas you might think you know your West Wing from your Oval Office, but think again.

In the basement at 1600 Pennsylvania Avenue, there are several rooms you would be surprised to find. As well as a bowling alley, there’s also a flower shop, carpenter’s shop and a dental surgery. It's a veritable mall down there.

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As one of New York’s most historic hotels and playground of high society, it's not surprising that the Waldorf Astoria is steeped in stories. It also has some mysterious spaces, including a secret station hidden below it...

An extension of Grand Central Station, track 61 was built in the 1930s to help President Roosevelt keep his polio diagnosis private while commuting between New York and Washington DC. Roosevelt's private train car hasn’t moved since his death in 1945, however, rumours swirl that the tracks are still in use by commanders-in-chief. Although, the hotel is currently closed for renovations.

Discover more abandoned subway stations around the world here

One of the most beautiful buildings on the planet, with the most romantic history, the Taj Mahal was built by the Mughal emperor Shah Jahān to immortalise his beloved wife Mumtaz Mahal after she died during childbirth. Inside the impressive building lie the cenotaphs of Mumtāz Maḥal and Shah Jahān, but all is not what it seems...

What many visitors don’t know is that in fact, these are false tombs; the real tombs lie beneath, at garden level, and are off-limits to the public. See more of India's most beautiful places here.

As the oldest part of the capital, the City of London is full of secrets – hidden lanes, peculiar signs and odd little buildings. But many of its most ancient secrets lie hidden beneath your feet – and the medieval Guildhall is no exception...

Visit the HQ of the Lord Mayor and you’ll find a horde of treasures including an ancient wonder. The remains of a once magnificent Roman amphitheatre, the largest in Britain, were discovered underneath the Guildhall Art Gallery in the 1980s. It’s free to visit.

Anyone that’s been will know that New York’s vast Grand Central Terminal is so much more than a train station. It’s a destination in its own right with shops, a food market, bars and restaurants. 

The historic terminal has also hosted sporting events including boxing during its history and has its own tennis club. The recently refurbished Vanderbilt Tennis Club can be found on the fourth floor. It first opened in 1965 and welcomes the public all year from 6am until 2am.

While most people visit Paris’ flagship museum for its works of art, the building itself is fascinating. It was originally built as a fortress in the 13th century by King Philippe Auguste and you can see the remnants of the original moat and tower base if you know where to look...

Archaeologists excavated the original moat 23 feet (7m) below the Cour Carrée during construction of the glass pyramid. Take a stroll through the medieval part of the Sully Wing to marvel at this age-old feat of engineering.  

The sprawling Piazza del Popolo is one of Rome’s most majestic and busy squares with three churches, pretty fountains and a large Egyptian obelisk. However, it wasn’t always such a convivial place. It is thought to have been built on the site of the infamous Roman emperor Nero’s family estate and his burial ground. According to medieval legend, Nero’s evil spirit haunted a tree on the site until the Vatican exorcised the area, cut down the tree and built the Santa Maria del Popolo, after which the square takes its name.

Opened in 1873 and designed by renowned architect Sir George Gilbert Scott, the prestigious Midland Grand Hotel was the epitome of a majestic railway hotel. While most people are aware of the sumptuously restored St Pancras Renaissance Hotel, which reopened in 2011 after decades of neglect, few know what else is tucked away...

There is a private apartment in its clock tower. With large Gothic windows and original 19th century iron staircases, the luxury space can be booked for private events and is open to tours once a year. There’s no fear about noise however, the bell chamber was designed as a folly. ​

Abu Dhabi’s Sheikh Zayed Grand Mosque is one of the world’s largest mosques: it can accommodate more than 40,000 worshippers, has 82 domes, more than 1,000 columns and is also home to a number of 24-carat gold gilded chandeliers. But among all the overwhelming interior opulence, the most luxurious element is somewhere you may never have looked: the floor.

The mosque is home to the world’s largest handmade carpet, which took 1,200 women two years to make. The carpet weighs a staggering 35 tonnes and measures more than 60,000 square feet.

A visit to the magnificent Art Deco theatre in Midtown Manhattan is on most New York visitors' wish list. While many people head there to see a spectacular performance by the Rockettes or to marvel at the splendour of the venue, very few know about a hidden apartment...

Left to gather dust for many years, the secret apartment given to theatre giant Samuel ‘Roxy’ Rothafel by the Rockefeller family in 1932 is now open to public tours and for private events. The wood-panelled Art Deco space in the eaves of the legendary music hall was where the mogul entertained peers such as Walt Disney, Judy Garland and Alfred Hitchcock but was largely forgotten after he died in 1936. Join a tour to hear about the famous faces and lavish parties that have been held at the Roxy Suite and to admire its glitzy interior, including lavish gold leaf ceilings.

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Built at the start of the 20th century, The Lincoln Memorial is dedicated to Abraham Lincoln. However, the great monument hides an equally giant secret. Below it lies a 43,800-square-foot underground chamber, known as the Undercroft, which contains graffiti from the 1910s.

The cavern, built to support the structures above, was forgotten about until the 1970s. It was briefly rediscovered and used for tours, before they were halted due to asbestos issues. There are plans to reopen the space in 2022, in time for the monument’s centennial celebration.

Located in The Hague, the Binnenhof is a group of buildings housing the Prime Minister of the Netherlands and is where all political matters are discussed. The Gothic-style buildings, which became the centre of the Dutch empire in 1584, make up the oldest Houses of Parliament still in use and is one of the country's most significant heritage sites.

Bibliophiles will be in seventh heaven in this cavernous library which lies hidden in the imposing Binnenhof. Sadly, the secret space – called the Handelingenkamer – is rarely open to the public. Complete with old-fashioned ladders, balustrades and a glass roof, which floods the room with natural light, the library was built in the late 19th century and houses volumes of verbatim reports of the proceedings and debates of Dutch parliament. 

Here are more of the world's most incredible libraries

Designed by Sir Christopher Wren as a ceremonial dining room in the early 18th century, the spectacular Painted Hall at the Old Royal Naval College has reopened after a £8.5 million ($10.5m) conservation project. As well as ogling at 18th-century artist Sir James Thornhill’s lavish wall and ceiling paintings, you can see two rooms from Henry VIII’s long-lost Greenwich Palace. They were unearthed beneath a concrete floor during the works. One was a cellar, which archaeologists believe may have been used to keep skeps (beehive baskets) during winter.

It might be one of the most famous and most photographed bridges in the world, crossed by millions, but few have been underneath it to see its inner workings.

Constructed below the River Thames, the cavernous Bascule Chambers are huge brick-line spaces used to house the counterweights when the bridge is lifted. Now the startling subterranean space is one of London's coolest and most covert venues for concerts and events. It is occasionally open for public tours too. 

Attracting tourists and locals alike, eager to see the Crown Jewels, learn about the ravens, the imprisonment and more, the historic Tower of London certainly captivates its visitors. But did you know you can also witness a 700-year-old ceremony that takes place within the walls of the Tower every evening?

Known as the Ceremony of the Keys, the traditional locking up of the tower by the Chief Yeoman Warder has taken place without fail for seven centuries. The exact same wording has been used by the sentry and warders for all these years, bar for the name of the reigning monarch. Tickets to watch this intriguing historic ritual are free but must be pre-booked.

 

The majestic Colossi of Memnon are one of many striking monuments on Luxor’s west bank. Built to guard the funerary temple of Amenophis (or Amenhotep) III, they are immense and captivating. But did you know these now faceless statues used to sing? It's thought an earthquake in 27 BC caused the northern colossi to crack which led to it emitting an ethereal whistling sound at sunrise. They were a top tourist spot for ancient visitors until a bodge repair job under the orders of Emperor Septimius Severus in the third century AD rendered them silent.

New discoveries have recently come to light at the site of Emperor Nero’s sprawling and opulent palace, the Domus Aurea, as a team of archaeologists unearthed a mysterious chamber. The underground room, which lay hidden for nearly 2,000 years, is rich in Roman frescoes including images of panthers, centaurs and a sphinx. It's thought the images were painted by imperial Roman craftsmen between AD 65 and AD 68.

With its fortress-like castellations and bell tower, Florence's Palazzo Vecchio is one of the city’s best-known landmarks. The town hall has a long and enthralling history and harbours many secrets including a hidden staircase added by the Duke of Athens for covert nightly exits. When Duke Cosimo I de’ Medici and his wife Eleonora of Toledo decided to turn the palace into their residence yet more secret routes and chambers were installed. You can discover some of the palace’s secrets on a special tour. 

The ruins of the once monumental city of Teotihuacán make up one of Mexico’s most enigmatic archaeology sites with many mysteries still surrounding its origin and demise. Last year archaeologists discovered a hidden tunnel leading to a chamber deep underneath one of its vast stone temples, the Pyramid of the Moon. Experts believe the ancient civilisation could have used the chamber for funereal rituals or ceremonies, and that the tunnel itself could have signified the route to the underworld.

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A gift from France to the United States to commemorate 100 years of friendship, the enormous Statue of Liberty is recognised around the world as a symbol of freedom. The statue, which is over 305 feet tall, is visited by around 3.5 million people every year. But there is a little-known fact about it...

There is an observatory inside the torch, the statue’s highest point. However, it’s strictly off-limits to visitors, and has been ever since 1916. That year, German spies blew up a nearby munitions depot and the resulting explosion caused significant damage to the torch. Although the damage has since been repaired, the torch has never been reopened to the public.

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