When visiting New York City there are a plethora of things to see and do. While the most famous attractions, such as visiting busy Times Square, going to the top of the Empire State Building or walking around the Natural Museum of History can be loads of fun, there are a ton of other less likely places to visit around the Big Apple.

Touring Manhattan can be quite overwhelming since there is an endless possibility of things to do. With hundreds of restaurants to check out, shows to see and hip bars to grab a cold beverage, there is always something to do. However, instead of hitting up one of the more crowded bars around Times Square, why not check out one of many secret speakeasies? We're sure your friends would much rather hear stories of the cool, lesser known places you've gone too than all of the more popular attractions.

We've come up with 20 secret underground places in NYC that you must see. These unique and one-of-a-kind places not only are some of the coolest places in the city, but also hold history that even New Yorkers might not know about. From a secret bar that's inside a Laundromat to a beautiful and old abandoned subway station that you can explore with friends, you'll be amazed that some of these places even exist in New York City.

20 Abandoned City Hall Subway Station

The City Hall subway station is the oldest and the most gorgeous subway station in New York City. Located downtown, the old City Hall station was built in 1904 but decommissioned in 1945 because its curving track could not be used with the city's longer and newer trains. The station is beautiful, built with Guastavino tile arches, (the same used in Grand Central Station), stained glass skylights, and brass lamps. You can take a tour of the station through the Transit Museum or take the 6-train going uptown and catch a quick glimpse of its beauty and wonder.

19 The New York Public Library Book Vault

The New York Public Library was built between 1902 and 1911 and at the time was the largest marble building in the United States. The library is the third largest in the world and is home to amazing and valuable treasures including William Shakespeare’s folios, Walt Whitman’s original copies of Leaves of Grass, and Jack Kerouac's manuscripts. Since 1987, the original Winnie-the-Pooh and his friends, Eeyore, Piglet, Kanga and Tigger have been living at the Library. Storage of books at the Library goes 30 feet deep under Bryant Park. So, if your ever sitting on the park's grass on a beautiful summer day, it's like you're literally sitting on treasure.

18 The Doyer's Street Tunnel

Back in the 1800's, Chinatown's Doyers Street Tunnel was used as an escape route for people fleeing gangs that pretty much ran the area. At the time, Chinatown was made up of alleyways used for gambling, smuggling, and the tunnel, for quick getaways. The tunnel is safe now, but the street was once called the "bloody angle" because the city's sharp curve allowed rival gangs to sneak up on one another. The 200-foot long street is even considered one of the most violent in American history. If you're visiting, make sure to also visit one of Chinatown's landmarks, Nam Wah Tea Parlor, the first business to bring Dim Sum to the city back in 1920.

17 Midtown's Hidden 25-Foot Waterfall

While it isn't exactly underground, this secret waterfall hidden in Midtown, Manhattan is a must see. New Yorkers have been taking the city for granted if they've never stopped to see this amazing 25-foot waterfall located on East 51st Street between Second and Third Avenues. This small patch of greenery is something you don't see among the city's tall skyscrapers. Named Greenacre Park, the park is privately owned by the Greenacre Foundation, and was a gift from the philanthropist Abby Rockefeller Mauze, the daughter of John D. Rockefeller Jr., but it is accessible by the public. Not only does it feature this gorgeous waterfall, there are also azaleas, pansies, a honey locust tree and chairs for people to sit and relax after a long day of work.

16 Radio City Music Hall's Secret Apartment

Everyone knows that Radio City Music Hall is the home of The Rockettes, and you've probably seen a show there, but did you know there is a secret apartment located in the building? The Art Deco-style apartment with 20-foot high ceilings covered in gold leaf was built for Samuel "Roxy" Rothafel, an entrepreneur who owned successful theatres in the city. Roxy would have some pretty famous people come over to his swanky apartment including Olivia de Havilland, known for her work in Gone With the Wind and The Adventures of Robin Hood and movie director Alfred Hitchcock. When Roxy passed in 1936, no one has lived in the apartment. Today, the swanky space is used for luxurious events.

15 El Sabroso

Step inside this industrial loading dock in Midtown, Manhattan, with a sign reading El Sabroso, and you'll find a simple food counter serving delicious Latin food, like stewed chicken or beef stew or roast lamb served with rice and beans on a paper plate. The meat comes right off the bone and the juices drip onto the yellow rice, making for one awesome meal after walking around the city. Not too many people know about this secret restaurant because it's pretty much tucked away, but you'll definitely want to give it a try if you are in the area. El Sabroso is located inside the freight entrance of 265 West 37th Street so don't miss it!

14 The Cloisters

The Cloisters is probably New York's best-kept secret museum located in Fort Tryon Park in Washington Heights. Sitting on the tip of Manhattan, you'll feel like you've stepped into a glorious castle with medieval gardens and over 2,000 pieces of medieval artwork from Europe. If you want to getaway from the busiest museums like the MET of the Natural Museum of History, take a cab ride to The Cloisters, which will take you away from the hustle and bustles of the city. The heart of the museum is the Cuxa Cloister and Garden with rose pink marble columns and a fountain at its center. The place is simply breathtaking.

13 Le Boudoir

Want to grab a cocktail while out and about in NYC? Skip all the busy hipster bars and head to Le Boudoir, a hidden cocktail bar inspired by the private chambers in Le Chateau de Versailles of Marie Antoinette. The bar channels 18th century France from its gilded mirrors and plush red velvet seating. The secret bar is accessed through a hidden door inside local French bistro Chez Moi at 135 Atlantic Avenue near Henry Street. The entrance to the bar is just as cool - a replica bookshelf which is one resembling one of the French queen's shelves from her library. After that, guests walk down a flight of stairs and enter the underground bar.

12 Green-Wood Cemetery, The Nation's Second Most-Visited Attraction

So you're not technically underground, but you get the hint here. Believe it or not, the Green-Wood cemetery in Brooklyn is the nation's second most-visited tourist attraction, right behind Niagara Falls. The cemetery is a National Historic Landmark and has over 560,000 residents, including Jean Michel Basquiat, William Magear "Boss" Tweed, Henry Chadwick and even Civil War generals. What makes this cemetery unique is it's amazing sculptures and it's beautiful scenery and you can't help but gasp as you look upon the Gothic revival northern entrance to the cemetery. You and your friends can take a historical trolley tour for just $15.

11 Track 61 Under Grand Central

We're pretty sure many New Yorkers didn't even know there's a secret train platform hidden deep in Grand Central. While it isn't in use today, it was a big help for presidents who wanted to escape the public and would enter the Waldorf Astoria Hotel without anyone seeing them. In fact, in 1944, President Franklin Delano Roosevelt used the train when he did not want the public to know that he was confined to his wheelchair after being diagnosed with Polio. The train is covered in bulletproof glass and thick steel, but sadly, after years of not being in use, it just sits abandoned underground. While it isn't open for the public for a tour, it is a cool part of American history that many people have no idea existed in the depths of Grand Central.

10 The New York Federal Reserve's Gold Vault

You would think that heading 80 feet beneath the New York Federal Reserve Bank in the Financial District to see more than 7,000 tons of gold bars would be highly restricted, but you can actually tour this spectacular vault and see the largest concentration of gold in human history. The vault is built in bedrock and contains deposits from central banks from around the world. Inside the vault are 122 separate mini-vaults and smaller vaults for account holders. And like we mentioned, there are about 7,000 tons gold bars, which comprise of five percent of all the gold ever mined. If you're interested in seeing this spectacular vault, you're going to need to register 30 days before you take a tour.

9 Sunshine Laundromat

Don't be confused by the dirty laundry and machines spinning clothes when trying to find the bar at the Sunshine Laundromat. Just step inside, make your way to the back, where you'll find what looks to be a stand alone dryer, push it open and you'll find yourself in a bar surrounded by nearly 30 arcade games. Games include an AC/DC Limited Edition pinball machine and classics like the Addams Family. There aren't any fancy cocktails or food here, just beer and wine and a bunch of games to play. So when making your way to this hip speakeasy, make sure you bring your quarters.

8 The Back Room

If you want to experience what may have been a real-life Prohibition-era speakeasy, then find The Back Room located on the Lower East Side. Drinks are served in teacups and bottled beers come wrapped in brown paper bags at this hidden bar. The space gives off a true speakeasy vibe, with furniture made of velvet, golden accents and a wood bar. To get into The Back Room, you have to go down the stairs of the "Lower East Side Toy Company," go through the back alley, then head up more stairs to the entrance. There's also a trick bookcase that leads to a VIP-only lounge.

7 Museum Of The American Gangster

The owner of this theatre found a number of tunnels in the basement, two safes, and $2 million in gold certificates, which were unfortunately expired. He learned that his theatre was a speakeasy run by gangster Walter Sheib. Today, there is a small museum located upstairs from the theatre rightly called, The Museum of the American Gangster. On display are one of the cracked safes, bullets from the St. Valentine's Day massacre, and medicinal prohibition whiskey. Also on display are a series of wires where Sheib rigged a bomb to the building in case of a raid. Check out this small museum dedicated to the gangsters who operated this speakeasy.

6 Trinity Place Bank Vault Bar

In New York's Financial District there is a hidden bar and eatery inside an old bank vault from 1904. Located at Trinity Place, this converted bank vault with original vault doors was commissioned by Andrew Carnegie and was the largest and strongest bank vault in the world at the time, weighing 35,000 tons. The bar and restaurant rests beneath the skyscraper and is something you don't see everyday. Much of the original structure and design are still intact and there is even a private meeting room the back that has been transformed into a dining space and an old elevator, which is now a wine cellar. Wouldn't you want to have dinner in a historic bank vault?

5 Garfunkel's

Another really cool speakeasy named Garfunkel's is located on the 2nd floor on Clinton Street above Barramundi bar. To access this hidden bar you have to locate the door that looks like a safe and you'll find a bar filled with upholstered furniture, bookcases and a candle lit living room where you'll relax in a crushed velvet armchair with drink in hand. This speakeasy gives off a very cozy and intimate feel and features a number of delectable cocktails. It's one of the city’s hidden treasures for a relaxing getaway if you don’t want all the fuss of a busy NYC bar.

4 Whispering Secrets Into The Walls Of Grand Central Station

Grand Central Station holds many secrets, one of which we already mentioned above that included a secret train station that president Franklin D. Roosevelt used. But there is also a whispering gallery located right next to the Oyster Bar & Restaurant that you must check out with a friend or loved one. This whispering spot is located in an unmarked archway and when two people stand at diagonal arches and whisper, they can hear each other's voices "telegraphed" from across the way. It's a cool thing that not many New Yorkers even know about. It was also rumored that jazz legend Charles Mingus proposed to his wife, Sue, this way.

3 Speakeasy Under The Woolworth Building

The Woolworth Building was the tallest building in New York City when it was built in 1913. Located in the Financial District, the building was once named the Cathedral of Commerce because of its Gothic features. What people don't know is that underneath the skyscraper is a speakeasy called The Wooly. Unlike the other speakeasy's we mentioned before with plush velvet seating and gold accents, this one is very hip, and feels like you're entering a Wes Anderson movie set. You'll find vintage sofas, paintings of animals, and lights saved from the Plaza Hotel. The speakeasy is only opened for special and private events.

2 Bowling Alley Beneath The Frick

The Frick Collection is an exquisite art museum located in industrialist Henry Clay Frick's former mansion on the Upper East Side of Manhattan. Walking through the mansion feels like you're attending a lavish ball and you'd never imagine that a bowling alley actually exists in an elegant place like this. However, hidden in the sub-basement is Frick's own personal bowling alley and installed the finest lanes at the time. Sadly, the public can't visit the bowling alley, but it's one cool thing to know that a bowling alley rests below a mansion decked in priceless art.

1 Holiday Nostalgia Train

If you're ever in New York during the holidays, between Thanksgiving to Christmas, you might end up taking a nostalgia subway train. These old, vintage trains, which are made up of subway cars that were in service from 1932 and operated until 1977, take you back in time. The subways run once a year, running from Manhattan to Queens. New Yorkers really get into the spirit of getting to take a ride on these old trains and dress up like people from that time. Riders get to see the similarities and differences between modern subway cars and those of the past. Even the ads inside the cars are vintage so you'll get the ultimate feeling that you’re taking a trip to the city in the 1940's. Visit the NY Transit Museum’s website to see when these spectacular trains come to life.

References: 6sqft.com, whalebonemag.com, yahoo.com,atasteoftravelblog.com,businessinsider.com, thrillist.com, atlasobscura.com, newyorker.com, nycgo.com