They’re some of the world's most recognisable and iconic buildings – yet there’s a surprising amount going on inside their walls that you might not be aware of. From the secret apartment atop the Eiffel Tower to the White House bowling alley, these are the spaces you're unlikely to find mentioned in your average guide book. 

Click through the gallery to discover the secrets harboured by the world’s most famous buildings...

One of the world’s largest mosques, Abu Dhabi’s Sheikh Zayed Grand Mosque has a number of impressive facts and figures associated with it. The grand structure can accommodate more than 40,000 worshippers, has 82 domes and more than a thousand columns, and is decorated with 24-carat gold plated chandeliers. But amid all the overwhelming interior opulence, the most luxurious element of all is somewhere you may not think to look: the floor.

The mosque is laid with the world’s largest hand-knotted carpet, which took over two years to create – eight months to design and 12 months for 1,200 workers to hand-knot it. Made in Iran, it arrived in nine parts that were assembled in the mosque, a process which took several more months. The carpet, laid in the main prayer room, measures 60,600 square feet (5,630sqm).

Disney’s Magic Kingdom opened in 1971 and was the first of the four Disney theme parks (and two water parks) in the Sunshine State. It’s where you’ll find the iconic Cinderella Castle (pictured) with its 18 towers and spires. But there's also a whole other side to the park that many people aren’t aware of and, by the time visitors have reached the castle, they’ve already crossed a network of secret tunnels and reached the third-floor level of a hidden city.

Underneath Disney’s Magic Kingdom is a vast, nine-acre network of hidden tunnels that’s only accessible to cast members. Walt Disney didn’t want the magical illusion spoiled by cowboys running through Tomorrowland or Mickey Mouse eating lunch in public. Therefore the so-called ‘utilidor’ system – made up of utility corridors or tunnels – was created to contain dressing rooms, rehearsal rooms and a cafeteria.

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The distinctive Sydney Opera House in Sydney Harbour is one of Australia’s most famous landmarks and on UNESCO's World Heritage List. It was opened in 1973, built to look like a yacht’s sails and designed by Danish architect Jorn Utzon. It hosts dance performances, concerts, opera and theatre shows. You can also take a guided tour of the building or eat at one of the restaurants.

What surprises people about the Sydney Opera House is that it’s not just an opera venue. In fact, there’s a ‘secret’ nightclub, The Studio, for dance nights, theatrical shows and underground music performances. It’s often used as part of the annual contemporary music festival, Vivid Live, and has hosted artists such as Tyler, the Creator.

La Sagrada Família is a very familiar sight in Barcelona, its striking design visible from many parts of the city. Construction of Antoni Gaudí’s Roman Catholic Church began in 1882 and it remains unfinished. An estimated completion date has been set for 2026, to coincide with the 100th anniversary of the architect’s death. Around three million visitors head to this breathtaking UNESCO World Heritage Site every year. 

While most visitors climb the many stairs, La Sagrada Família has a set of secret lifts that can take you straight to the top. This is a surprising feat when you consider the narrowness of the towers – not to mention the fact they’re not built in straight lines. Once you’ve reached the top you can enjoy excellent views across Barcelona, breath still intact.

Opened in 1922, the Lincoln Memorial is dedicated to the 16th President of the United States, Abraham ‘Honest Abe’ Lincoln. The memorial’s frieze has inscriptions of the 36 states in the Union at the time of Lincoln’s death, along with the dates when they joined. It's free to visit as part of the larger National Mall, which also includes the Reflecting Pool, the Washington Monument and the US Capitol.

However, the great monument hides an equally great secret. Below it lies a 43,800-square-foot (4,069sqm) underground chamber known as the undercroft, which contains graffiti from the 1910s. The cavern was built at the same time as the memorial to support the structures above, though was largely forgotten about until the 1970s. It was then briefly used for tours before they were halted due to asbestos issues. Work is now underway to transform the space into an immersive museum dedicated to the history of the popular monument with an opening date scheduled for 2026.

One of the world’s most famous and instantly recognisable structures, the Eiffel Tower has welcomed over 300 million visitors since it opened in 1889. It was once the world’s tallest man-made tower and weighs more than 10,000 tonnes. Yet, despite the millions of visitors who flock here each year, the Parisian icon still manages to keep some surprises concealed within. Most visitors, for example, don’t know the tower is home to a small apartment.

Designer Gustave Eiffel, who dreamt up the construction, also built himself a flat just below the tower’s spire. Complete with wooden furniture, oil paintings and patterned wallpaper, the apartment was reportedly in demand in Parisian high society in the 19th century. People offered Eiffel large sums of money to rent the space even for one night, though he apparently never relented and it was primarily used as an office. It’s now an area for technical facilities with a recreation of the apartment complete with waxworks (pictured).

One of the world’s most beautiful buildings with the most romantic and tragic history to go with it, the Taj Mahal was built between 1632-53, having been commissioned by the Mughal emperor Shah Jahan to immortalise his beloved wife Mumtaz Maḥal after she died during childbirth. It’s incredibly lovely, especially when viewed at sunrise or when bathed in moonlight, when the ivory marble is at its most dazzling.

Inside the impressive building lie the cenotaphs of Mumtaz Maḥal and Shah Jahan. However, what many visitors don’t know is that these beautiful monuments, housed in an ornate chamber, are empty. The real tombs are hidden beneath, at garden level, and are off-limits to the public.

Mount Rushmore National Memorial is one of the USA’s most recognisable sights. Completed in 1941 after 14 years in construction, it consists of four 60-foot-tall (18m) faces of legendary American presidents – George Washington, Thomas Jefferson, Theodore Roosevelt and Abraham Lincoln – carved into granite in South Dakota’s Black Hills. While it’s technically a sculpture rather than a building, it does harbour a secret room...

One of the famous faces conceals a secret: Lincoln’s visage is right in front of a hidden corridor. Originally planned to be part of a Hall of Records – designed to store important documents in American history for future generations – the full construction was never completed. It was only in 1998 that the National Park Service added a repository of records which were placed in a teakwood box inside a titanium vault, to fulfil part of sculptor Gutzon Borglum's original vision.

The towering Burj Khalifa pierces the sky at a staggering 2,717 feet (828m). It holds world records for not only being the tallest building in the world (for now), but also the tallest man-made structure in the world, the tallest free-standing structure in the world and the highest outdoor observation deck in the world. People can book tickets to explore the lofty tower and take in incredible views over the city.

However, while you might have heard about the Burj Khalifa’s swanky residences, Armani Hotel, corporate suites, five swimming pools, health club and spa, what many people don’t know is that the record-breaking building is also home to a private library. The world’s highest library, in fact, this quiet space is tucked away on Level 123.

One of the world’s most famous train stations, Manhattan’s Grand Central Terminal first opened in 1913 and still puts most other train stations to shame with its beautiful architecture, huge range of shops and restaurants and visitor numbers – approximately 750,000 a day. It’s the second-most visited destination in New York City after Times Square.

But as well as being a great shopping and dining destination, the station houses a luxury tennis club unknown to many of the commuters and tourists that usually rush through this station daily. Vanderbilt Tennis Club, tucked away on the fourth floor of the terminal, is a super-swanky fitness destination with courts, available to book by the hour, edged by the top of the station’s signature arched windows.

It has starred in countless movies, offers exceptional views across New York City and was once the tallest building in the world. The Empire State Building, an architectural marvel when it was built between 1930-31, plays host to millions of visitors every year, but most are unaware of the Art Deco tower's big secret.

While most visitors enjoy the views from the building’s 86th and 102nd floor observatories, there’s another, higher level reserved for VIPs, dignitaries and celebrities: the 103rd floor. Entertaining the likes of Taylor Swift and David Beckham (pictured), the balcony is reached by a secret door and some rather narrow steps.

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While the exclusive balcony might provide all the views, head down into the basement and you’ll find a fascinating glimpse into the building’s past. Some 35 feet (11m) underground is a huge abandoned vault, which belonged to a bank that rented out the Empire State Building’s second floor. The vault still has its original steel ceilings, though its stash of safety deposit boxes was removed in the 1990s.

Melbourne’s Flinders Street Station is one of the city’s most beloved buildings. The first railway station built in an Australian city, the terminal has appeared in a number of movies and is well-known for the old-fashioned clocks displaying train departure times on its facade. The present building was constructed in 1905 but there was a station – of sorts – here from 1854, a ramshackle series of weatherboard sheds.

But visitors rushing to catch their trains probably won’t notice or even be aware of one of the most fascinating features of the train station: its secret abandoned ballroom. On the third floor of the building, the once-opulent ballroom hosted concerts, competitions and public dances in the 1950s and 60s. However, it stood empty for decades after the last dance in 1983. As part of major renovations to the historic station in 2019, the moth-balled ballroom’s damaged ceiling was restored and the room made safe. It has since been used as a venue for art exhibitions. 

New York’s Waldorf Astoria is a temple of classic hotel luxury. The historic establishment, which first opened its doors on swanky Park Avenue in 1931, has hosted royalty, presidents and film stars in its lavish rooms and beautifully decorated spaces. It’s been closed for extensive renovations with new suites added and event venues, restaurants and common areas being refreshed – check the website for the latest updates on reopening.

Underneath the opulent hotel lies something rather less glamorous and very unexpected: a disused railway station, known as Track 61. Everyone from presidents to military officials and celebrities are rumoured to have used the track in order to avoid being bothered by the press or members of the public. For a long time the underground platform was home to a train car (pictured) said to have transported President Franklin D. Roosevelt, although it has now been moved to the Danbury Railway Museum in Connecticut and there are suggestions that it was in fact nothing more than a baggage car. 

One of the city’s most iconic sights, Edinburgh Castle looms above the Scottish capital on Castle Rock. It has been occupied from as early as the Iron Age and is one of the most besieged castles in the world. It’s an active military garrison as well as a tourist attraction (you can buy tickets online): a gun is fired from the Mills Mount Battery at 1pm every afternoon except on Sundays, Christmas Day and Good Friday.

The castle has a number of myths and legends surrounding it, many pertaining to its military past and present – the most famous being an alleged secret tunnel running from the castle to the Palace of Holyroodhouse beneath Edinburgh’s Royal Mile. If it truly exists, the tunnel has yet to be discovered. However the castle does have a more tangible, and very touching, secret above ground: a dog cemetery for regimental mascots and beloved pets of high ranking soldiers. Visitors cannot enter, but it is possible to view the cemetery from above. 

Located in The Hague, the Binnenhof is a group of buildings, including the office of the prime minister of the Netherlands, and is where all political matters are discussed. The Gothic-style buildings, which became the political centre of the Dutch Empire in 1584, make up the oldest houses of parliament still in use. It’s also one of the country's most significant heritage sites.

Binnenhof is also home to an enormous library that looks like something from a fairy tale. The secret space is called Handelingenkamer or Old Library and it’s rarely open to the public. It holds more than 100,000 volumes containing the official verbatim reports of parliament. The stunning library has old-fashioned ladders and a glass roof that floods the room with natural light.

The Supreme Court of the United States in Washington DC is the country’s highest federal court. Established in 1789, it deals with a narrow range of cases where federal law is involved. It’s open to the public Monday to Friday (except Federal holidays)  from 9am to 3pm.

You may not be aware that this otherwise austere building also has a lighter side. The fifth floor is home to another type of court: a basketball court nicknamed ‘The Highest Court in the Land’. It occupies what was once a spare room used to keep journals and became a workout space in the 1940s, with baskets added later on. It’s usually used only by the building’s employees although no play is allowed when the main court is in session.

The Monument to the Great Fire of London – better known as simply the Monument – was completed in 1677 as a permanent reminder of the Great Fire of 1666. It soars at 202 feet (62m) in the City of London, just north of London Bridge. Hundreds of thousands of visitors climb its 311 spiral steps each year to enjoy views over England’s capital.

The building, designed by Sir Christopher Wren, isn’t just a monument or a way of getting a great view of the city. It was designed to double up as a huge Zenith telescope for gravity and pendulum experiments. There’s even a small laboratory underneath the building where scientists would peer through the telescope. This use was quickly abandoned, though, because the surrounding area was just too busy.

A gift from France to the United States in 1886 to commemorate 100 years of friendship, the enormous Statue of Liberty is recognised around the world as a symbol of freedom. The copper statue, more than 305 feet (93m) tall, is typically visited by around 3.5 million people every year. People can access various parts including the museum, theatre, pedestal and crown.

A little-known fact about the Statue of Liberty is that there is an observatory deck around the torch. Only ever accessible to VIP guests, it has been off-limits to all visitors since 1916. That year, German spies blew up a nearby munitions depot and the resulting explosion caused significant damage to the torch. It fell into disrepair and was eventually replaced in 1985. The original torch can now be viewed in the Statue of Liberty Museum.

One of London’s most recognisable landmarks, the Gherkin (officially 30 St Mary Axe) towers over the city at nearly 600 feet (183m) tall. The building, designed by Sir Norman Foster, was completed in 2003 and contains offices, shops and restaurants. The most notable, Helix by Searcys, is a 360-degree restaurant with a bar, Iris, spread across three floors.

It’s known for the curved appearance that earned its nickname, though some might be surprised to discover another fascinating element of its architecture. Nearly 5,500 panes of glass – enough to cover five football pitches – were used to build the landmark. However, despite its rounded look, there’s only one piece of curved glass on the entire building: the dome at the top.

The White House was built in stages between 1792 and 1829. Every president since John Adams in 1800 has lived here. Getting a tour of The White House is extremely difficult to arrange: Americans must go through their state’s member of Congress and non-Americans through their country’s embassy in Washington DC. Fans of US political dramas might think they know their West Wing from their Oval Office, but the building still has a few surprises.

Harry Truman opened a basement bowling alley in 1947, though it was moved next door to what’s now the Eisenhower Building in 1955. Richard Nixon added a new one-lane alley beneath the North Portico entrance of 1600 Pennsylvania Avenue two years later, although he is pictured here in the earlier version. The basement also has a flower shop, where all of the building’s bouquets are prepared.

Officially named the Elizabeth Tower, the clock tower of the Houses of Parliament is known the world over as Big Ben. That moniker is itself a nickname for the Great Bell, one of five bells within the tower, which recently underwent major conservation work to restore it to its former glory. Cast in the 1850s, the bells have tolled across London as seven monarchs and 46 prime ministers have come and gone. 

Despite its iconic status, Big Ben is far from perfect. In fact, it’s cracked. In 1859, a new bell that had replaced a previously broken one also cracked, meaning Big Ben didn’t chime for four years. Instead of installing a third new bell, it was turned so the hammer struck a different spot. The hammer was also replaced by a lighter version and a square was cut into the bell to stop the crack from spreading.

Designed as a small fortress at the end of the 9th century and used as a residence for the Nasrid Dynasty in the 1200s, the Alhambra was the last of the Moorish Muslim states to be conquered by the Spanish Catholic Monarchs in 1492. Renowned for its stunning Islamic architecture, today the complex is a popular tourist destination. However, there are secret sections that are off limits…

The throne room is visited by thousands of people every year, but few are likely to know that below it lies a more humble gallery that would once have housed guards on constant lookout. More mysterious are the networks of tunnels and caverns beneath the Alhambra complex. Some may have been used to store grain, others were clearly dungeons. Historians think they may have been used to house important prisoners for ransom or exchange.

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