6 Vanderbilt Tennis Court is an unnoticed tennis court in the Grand Central Terminal that has existed since the 1960s. There is one full-sized court, a junior court, and a fitness room located in the upper levels of the terminal.

Approximately 750,000 people pass through the Grand Central Terminal every day including the locals. But only the rarest of people are aware of the presence of hidden, although accessible, tennis courts. 

Geza A. Gazdag was a Hungarian immigrant who founded the Vanderbilt Athletic Club on the third floor of the terminal. He named the place after Cornelius Vanderbilt who originally built the Grand Central Depot. 

In 1984, Donald Trump tried to convert the place into a private tennis court where celebrities and wealthy tennis enthusiasts could play. Trump renovated the sports court and annexed it into an uber-exclusive court. 

The semi-secretive court operated for 30 years until Trump’s lease expired. The Grand Central ran without a tennis court for a couple of years, and the court was shifted to the fourth floor in 2011. Services of the new court are obviously cheaper than the Trump’s courts. 

The courts could be used by the public, but tracking and booking slots are subject to a complicated process. 

The main court at the membership-free club is the only court in New York that includes on-court, slow-motion video analysis. (1, 2)

7 A lot of people don’t know about a secret observation deck on the 103rd floor of the Empire State Building in New York. To reach the balcony, one needs to take a series of elevators and then a very steep, narrow staircase. The deck isn’t open to the public, although several celebrities have been photographed here. 

The 103rd floor lies on top of the officially recognized top floor, or 102nd floor, of the Empire State Building that is accessible to the public. The secret deck is extremely terrifying to gaze out from.

The regular floors on the building have safety devices to ensure that nobody falls from the building, but the secret one has just a ledge topped with a low railing. People have reported that their feet and hands tingle and you sweat when having a look down. 

When the wind blows, it almost feels like it will take it with you, although the deck is surely one of the most special places in New York City. 

To reach the place, first, the person needs to take a series of elevators past the inner workings of the buildings like electricity boxes and pipes. It is mostly visited by celebrities, and opening it to the public would result in a complete disaster. 

The uppermost floors, or the 102nd and 103rd floors, are placed on the 200-foot metal tip which was originally supposed to be a morning mast for airships. (Source)

8 Michelangelo, the artist, hid in a tiny secret room under the Medici Chapel of the Basilica di San Lorenzo in Florence to escape the wrath of the Pope in 1530. He spent three months sketching on the walls with charcoal that were lost for almost 500 years. The museum director discovered the drawings only in 1976. 

When all hell broke loose in Florence, the artist was left with nothing but time and charcoal in his hands, so he covered the walls with prisoner graffiti. He had designed the Chapel as an elaborate, domed mausoleum for his patron family. 

During the three months of hiding, he drew himself, Christ, and images from the ceiling of the Sistine Chapel which he had completed in 1512. Michelangelo would have been punished along with the other republicans if he had not hidden for three months. 

In November 1530, the artist was reassigned to complete the Chapel. He never revealed his hiding place, and it was a mystery for 500 years. Some believed that he took cover at his friend’s or in a church bell tower. Since the drawings were found in 1976, the place is alternatively closed and open for the public. (Source)

9 Behind the carved heads of Mount Rushmore, there is a hidden vault that contains the text from the Declaration of Independence, the Constitution, and the Bill of Rights. The “Hall of Records” is behind Lincoln’s hairline and inaccessible to the general public. 

The doorway that leads to the secret room can be found at the frontal lobe of Lincoln’s brain. Gutzon Borglum, the sculptor of the monument, had originally drafted 800-foot stairways leading to the hall measuring 80 by 100 feet. 

It would have featured legendary works of famous Americans and a list of US contributions to science, art, and industry. 

The idea of making the grand hall died with the sculptor in 1941, although, in 1998, officials placed a record of the country’s history inside the unfinished hall. Inside the room, there’s a small wooden box that contains US’s significant documents including Borglum’s biography. 

The design of the hall currently is way different from what the sculptor had originally imagined. It is closed to the public. The closest one can get is its doorway at Lincoln’s head. (Source)

10 A capsule was placed on top of the Gateway Arch on 28 October 1965 that holds 762,000 signatures and a piece of residential history. The capsule is hidden by permanently welding inside the arch, and the list of signatures is not public. It is believed that the capsule will not be opened as long as the monument stands. 

The Gateway Arch located in St. Louis, Missouri is 630 feet tall making it the tallest arch in the world. Its construction was completed in 1965, and since then, it has been a popular tourist destination. It is a weighted steel catenary arch which is designed by Finnish-American architect Eero Saarinen. 

The existence of the capsule remained a secret until workers made the news public. People have visited the monument time and again, but nobody was lucky enough to witness the capsule present at the top. 

The workers who reported the capsule mentioned that there were more than 700,000 signatures present on it. Most of these belonged to the people of St. Louis of which 1,500 were schoolchildren. 

The opening ceremony of the monument was initially scheduled for 18th October. However, its construction wasn’t completely done then, so the date was rescheduled to the 28th. The capsule was welded inside the arch sometime during these 10 days. (1, 2)