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Empire State Building, NY - The famous New York monument appears, to the regular eye, to end on the 102nd floor. In truth, there's another floor! 

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Empire State Building, NY - It's a small room with a balcony that requires a series of elevators and then a steep, narrow staircase to get to. Technically only staff can go up, but the occasional celebrity has slid by. 

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Gateway Arch, MO - A trip to St. Louis is only complete once you've seen the Gateway Arch. It's the tallest man-made monument in the country, soaring at a lofty 630 ft. Can you guess what's hiding in the keystone?

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Gateway Arch, MO - A time capsule! It contains the signatures of 736,000 local residents (mostly school children), a newspaper, stories by local writers, and some other mystery items.

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Statue of Liberty, NY - Gifted to the US by the French government, most people know that this landmark functioned for a while as a beacon of hope for newcomers as well as an actual lighthouse. 

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Statue of Liberty, NY - What most people don't know is that there is a hidden room in Lady Liberty's torch! People could visit it up until German agents blew up a nearby pier and damaged the staircase in her arm. 

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Statue of Liberty, NY - People are also usually savvy to the fact that the seven rays of her crown represent the seven continents, signifying that freedom is a universal ideal. But there’s one thing nearly everyone misses.

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Statue of Liberty, NY - The statue's feet are hard to see, so people often don't notice that she stands amid broken shackles, and that her right foot is raised to show that she is moving away from oppression.

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Disneyland, CA -

Disney has become a famous American landmark over the years, and while even hardcore fans might know some secrets of the park, very few are privy to the prestigious and secret Club 33.

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Disneyland, CA -

The exclusive restaurant is hidden behind an unmarked door in the New Orleans Square, and it's the only place in the park that sells alcohol. But don't book your trip unless you have the $25,000 required to join the club, plus the minimum annual fee of $10,000.

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Grand Central Terminal, NY - The popular New York landmark where everyone seems to be in transit is also a destination point! The Campbell, a bar and lounge, is a hot secret located in the terminal.

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Grand Central Terminal, NY -

Its vaulted ceilings, stone fireplace, century-old leaded glass, and high-end cocktails pay homage to a Jazz Age financier who converted the space to a reception hall in 1923. It's also a popular celebrity destination! 

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Grand Central Terminal, NY - Even more surprising, and something most people wouldn't guess, is that the fourth floor of the terminal has hosted the Vanderbilt Tennis Club since the 1960s! It has one full-sized court, a junior court, and a fitness room.

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Mount Rushmore, SD - The monument to four American presidents carved on Mount Rushmore was designed by Gutzon Borglum, who initially wanted to include a written description of the nine most important events in US history.

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Mount Rushmore, SD -

Borglum was only approved to create a Hall of Records, a chamber intended to hold some of America's most treasured documents, behind the hairline of Abraham Lincoln. Unfortunately, the sculptor died before completion.

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Mount Rushmore, SD - Still, behind Abraham Lincoln’s head is a chamber which reportedly includes a vault that holds biographies of the four figure heads, copies of the Declaration of Independence, Constitution, and Bill of Rights, and other historical artifacts.

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Lincoln Memorial, Washington, D.C. - This monument is remarkably rich with symbolism, but too many visitors often fruitlessly search the back of Lincoln’s hair for an image of Jefferson Davis that some historians insist is hidden there.

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Lincoln Memorial, Washington, D.C. - What there is, however, is a typo in Lincoln’s Second Inaugural Address, chiseled into stone. He apparently had “high hope for the euture.” The 'E' was eventually filled in to look more like an 'F,' but it's still obvious. 

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Lincoln Memorial, Washington, D.C. - Even cooler is the message in the upright bundles of rods below Lincoln's wrists, called fasces. They're ancient Roman symbols of power, following the idea that rods bound together are stronger than one rod alone. Try to spot them around the monument!

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The Alamo, TX - The TV show 'Unsolved Mysteries' excavated an old well at the historic site based on an old map that has spread rumors of buried treasure. No treasures were found, but the whispers persist. 

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The Alamo, TX - It's also believed skulls and bodies of the site's defenders were buried there, and the building has been plagued with rumors of ghosts and unusual noises for over a century now. 

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Washington Monument, Washington, D.C. - Back in 1848 when the obelisk was being erected, items were hidden in its structure! They included a copy of the Holy Bible, a copy of the US Constitution, a portrait of Washington, and every US coin from the time.

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Washington Monument, Washington, D.C. - A message hides 550 ft above these hidden items, engraved in the aluminum pyramid at the very tip of the monument. The words are “Laus Deo!,” meaning Praise Be to God.

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Golden Gate Bridge, CA - The secret of this West Coast landmark lies within coats of paint. Though it's commonly thought to be red, the paint color is actually called ‘International Orange.’ The color was reportedly an accident that was originally used as a primer, but it looked nice and remained visible in the fog, so the bridge’s architect decided to keep it!

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Niagara Falls, NY - Just down the gorge from one of America’s most popular tourist destinations lies the Cave Of The Evil Spirit, a hidden limestone cavern with a spooky history dating back over three centuries.

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Niagara Falls, NY - The cave was named by Seneca American Indians, and is said to be above the site of the 1763 Devil’s Hole Massacre. Legend says that anyone entering the cave will meet a painful demise.

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Fort McHenry, MD - So you may have known that this monument was constructed in the shape of a star, and that its flag inspired the national anthem back in 1812, but did you know it's tradition to fly every new iteration of Old Glory over the fort?

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The Hoover Dam, NV -

The underground facility beneath the dam is a hot spot for conspiracy theories, but even weirder is that dozens of bodies are believed to have been buried within the concrete structure, as there were over 100 deaths during its construction.

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Track 61 under the Waldorf Astoria, NY -

An antique train car is still parked in the tunnel beneath one of New York City's most luxurious hotels. Rumor has it, the abandoned track is still used to transport celebrities and other notable guests to and from the hotel. 

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CIA headquarters, VA -

An artist named Jim Sanborn created this sculpture called Kryptos, and while many have tried to solve the encrypted message, it still remains one of the most well-known unsolved codes in the world.

See also: Strange facts you didn't know about the US Constitution

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