When workers were renovating the Lincoln Memorial for a major event, they discovered something totally bizarre, right beneath their feet. It turned out that Honest Abe was sitting atop a massive secret — literally. If you’ve ever set foot on the Tennessee pink marble floors and stared up at the stoic expression of America’s 16th president, you were actually standing right above a decades-old secret passage that few knew existed.

A construction crew working at the Lincoln Memorial back in 1975 was tasked with renovating the bathrooms. However, not long into their project, they noticed something strange about the structure’s foundation that no one was prepared for.

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When workers took a closer look at the foundation, they discovered a massive room beneath the chamber housing Lincoln in his chair. As anybody else would do after discovering a major historical secret, the construction crew quickly told their friends.

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A few of those buddies were members of the National Speleological Society, who explored the giant room with awe. Stalactites and stalagmites formed during the years that space was neglected; they viewed it as sort of a manmade cave.

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The room was massive: 43,800-square-feet to be exact. The more they poked around, the crazier and eerier the Lincoln Memorial basement revealed itself to be. Besides the rats, insects, and general spookiness, its mere existence sort of creeped everyone out.

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How was it possible, that one of the most iconic monuments in America, with over 7 million visitors file through its chambers each year, kept its gigantic basement a secret? Surely, the room had once served a purpose.

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Construction for the Lincoln Memorial kicked off in 1914. This is what the Potomac Park area looked like prior to breaking ground on the project. It took 40 years for the Army Corps of Engineers just to create the shoreline that serves as the attraction’s backdrop.

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The project necessitated that they first dig 40 feet down in the earth. In order to support the rest of the structure, they had to install a series of concrete pillars. When they were finished, it looked like a cathedral all on its own.

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But after the crew proceeded with the rest of the 19-foot statue and the 145 steps leading up to it, the underground chamber just slipped from everyone’s minds, since it was no longer needed.

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Once the National Parks Service got wind of the Lincoln Monument’s killer basement, they had to show it off. Without much preparation, the derelict space was opened to the public, and tours of amazed visitors shuffled through its cavernous passages.

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If you visited the memorial between the mid ’70s and late ’80s, you might have seen the big old basement for yourself. Officially, this space is called the undercroft, but it’s still relatively unknown to the general American public.

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Knowing that people were allowed to traipse through this elusive passageways for a while, why did they eventually shut it down? Well, it wasn’t exactly safe. During one tour, someone spotted what looked like asbestos in the basement.

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In 1989, the undercroft was shuttered to the public. The National Parks Service needed to take care of the asbestos situation, and probably realized that the space was generally unfit for tours. Still, it wasn’t as forgotten as it once was.

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Over the years, select lucky adventure seekers have glimpsed the insides of the Lincoln Memorial undercroft, witnessing its most special feature — graffiti. Many of the columns in the basement are covered in funny little illustrations.

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Steven Schorr, the president of DJS Associates, — a forensic consulting firm that took scans all over The National Mall and Lincoln Memorial — said, “The builders actually drew cartoons and they have them covered in Plexiglas.”

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Drawing silly pictures on the pillars of a presidential memorial must have felt like the most rebellious act on the construction site for those 1914 laborers. Nearly a century after its completion, though, those cartoons are becoming the focus of the display.

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Billionaire philanthropist David Rubenstein has invested a staggering $18.5 billion into a project to modernize the Lincoln Memorial, including the undercroft space, allowing more Americans to glimpse that forgotten part of history.

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The project marks the largest renovation the memorial’s had since it first debuted in 1922. For Rubenstein, he views his ability to make this contribution to the Great Emancipator’s monument as a tremendous honor.

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The plan is to reopen the undercroft to the public for the Lincoln Memorial’s centennial in 2022 if everything goes according to schedule. So in the next few years, you might be able to walk among the storied columns for yourself!

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For those planning to visit the Lincoln Memorial anytime soon, sadly, the undercroft remains off limits. Though, you can reportedly see the coordinates that mark the entryway into the chamber. If you want to impress any employees, ask about the basement.

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Parks services employees had no clue that there was a hidden cathedral underneath the Lincoln Memorial, which is actually quite common for historic building projects from the turn of the century. The New York Public Library also had a curiosity included in its construction, that most people still don’t know about.

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The lore of New York City Public Library system is lengthy and packed with wealthy investors, including one Andrew Carnegie. In 1901, the steel tycoon donated 5.2 million dollars to the City of New York for the construction of sixty-five new library branches.

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Coal furnaces were the heat standard at the time of construction for the Carnegie branch libraries. Tending to the furnace was an around the clock job, a consideration that was included in the blueprints for each build.

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That required each of the Carnegie library branches to employ a custodian, who lived right on-premises. These caretakers and their families called the library their homes. In most cases, on the floor above the stacks of books was a fully furnished apartment.

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One of the individuals who shared an address with the library was John H. Fedeler. He lived in the flagship location on 5th and 42nd street for thirty years, and that wasn’t even the most interesting thing about him. Fedeler was also a Harvard educated inventor who dabbled in prize fighting.

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The prospect of working and living inside a library attracted all sorts of interesting open-minded individuals. Who wouldn’t want to shuffle slipper-footed through the stacks on a Sunday night? It was a truly unique career opportunity, but as time passed, the job became less necessary.

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By the 1980s, all the apartments inside Carnegie branch libraries were empty, as coal heat was long since replaced by electricity and gas. Plus, the entire function of a public library had changed, with modernization and technological advancements.

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Given the value per square inch, these libraries couldn’t afford to preserve a space simply for nostalgic and historic purposes. Despite how fascinating and well preserved these apartments were, many had to be renovated into media centers and storage space.

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Of the 65 Carnegie library apartments that once existed, only 13 remain. To some, they might just look like any other dilapidated space, but for those who know about these secret hideaways inside the libraries, they’re pretty dang cool. Maybe too cool?

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In fact, many within the library system don’t even know about these concealed apartments. Iris Weinshall only became aware of the neglected living quarters upon taking up her post as CEO of the New York Public Library. 

The entrances to the Carnegie library apartments are intentionally hard to spot. Usually, there’s a nondescript door that leads to a stairway. Inside, the apartments share some of the design elements of the space below, like large windows, but lack the same decorative touches, like elaborate molding.

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Perhaps the most glaring sight that hits you upon entering the library apartments is their plain spookiness. Many of them look warped by time — cobwebs, water damage, peeling paint — making them an ideal setting for a horror film. One looks particularly scary.

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The Fort Washington library opened its doors to the public and the new resident of the third floor apartment back in 1914. Of all the Carnegie library branch apartments, this is the largest and most elaborate.

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Grand in size and eerie details, the Fort Washington apartment has an extra special feature that some call a dumbwaiter. but is more aptly labeled as a death chute. Today, it only functions as a curiosity.

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Walking through the apartments, you notice traces of those who once called the space home. The family that inhabited the Fort Washington apartment had a flair for bold, bright colors.

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Ronald Clark was a teen when his family moved from Maryland for his father to take a job as a live-in library custodian. It took some getting used to, and he had to shrug off his initial angsty embarrassment, but he later realized how unique his family’s experience was.

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All of Ronald’s friends would constantly brag, “This guy lives in the library. Literally—he lives in the library!” He grew to have tremendous pride in his unconventional home and took advantage of the endless supply of books.

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The Washington Heights branch apartment where Ronald Clark lived had a 4.4 million dollar renovation for library programming. As the guest speaker at the ribbon-cutting ceremony for the refurbished space, he shared how much the library meant to him and his family.

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Ronald Clark’s daughter Jamilah also lived in the library until age five. She explained how it formed her perspective, “I didn’t even have the concept of library, just that I lived in a place with tons of books, everywhere, and I could read them and play with them.”

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Some book worms out there would gladly swap a few million for the opportunity to live in the library. Especially in a space with quaint historic charm and large original windows, even if it requires a lot of elbow grease.

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Just add it to the list of crazy New York oddities that even most lifelong residents haven’t heard of. No matter where you are in the five boroughs, you’re not far from a wacky bit of history that usually goes unnoticed.

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1. The World Trade Center (rest in peace) used to be a center for literal trade. Called Washington Market, tons of vendors would set up stalls, hawking items such as produce and dairy as well as odder items, including llama and bear paws.

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The bustling market lasted a ways into the 20th century, even as competition from other businesses grew. It was only once the 1960s came along that the city demolished the popular spot to make way for the ill-fated Twin Towers.

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2. Everyone is familiar with LA’s Hollywood Walk of Fame — you know, the glitzy stars emblazoned into a stretch of the celebrity-addicted city. But few were aware that New York City has one of its own, albeit slightly less polished than the one in California.

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In 1971, a theater owner got some of his closest starlet pals to place their hand-prints into wet cement on the notoriously gritty St. Marks Place sidewalk. Famous people including Myrna Loy, Gloria Swanson, and even Joan Crawford participated. Many of the historic markings still remain.

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3. There are tons of skeletons buried underneath the city. One of these mass graves was discovered in 1991 when workers digging near city hall happened upon the remains of one African Burial Ground — a place freed slaves had been laid to rest for centuries. The memorial in their honor is pictured below.

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But this isn’t the only place where skeletons lie. Recently, construction workers installing pipes under Washington Square Park stumbled upon some bodies of their own. Apparently these ones had been placed there centuries prior, likely by the former Cedar Presbyterian Church.

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4. It’s a little-known fact that Aaron Burr, Vice President to Alexander Hamilton, actually died alone in a Staten Island hotel. Certainly tragic circumstances for the famed politician, but the events that transpired after he had passed are even eerier.

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After people became aware of the specific room that he died in, many guests specifically requested to stay in it (like, are you trying to be haunted?). The place doesn’t shy away from the publicity either, even posting a plaque outside saying “Aaron Burr died here.”

5. The iconic New York Public Library used to dish out something vastly different from books. In the 19th century, it was actually a huge reservoir that served as the main source of water for over half of the city’s population.

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The situation went downhill for the water source when a second reservoir opened in Central Park and the first had started leaking. This all led to its demise, allowing the city to begin construction on its famous lion-guarded library in 1895.

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6. Starting in 1897, much of New York mail was delivered through large tubes that shuttled letters and packages into canisters that were located around the city. Unfortunately, while this system seems super cool, it reached its end for a sad reason.

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At the tube system’s highest point, at least 30% of city-dweller’s letters were being sent through this odd machinery. However when World War I came around, officials decided they just couldn’t afford the cool gadgets anymore and shut them down for good.

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7. While it seems like a no-brainer that the Statue of Liberty is green, it actually wasn’t always that way. Its creator, Frédéric Auguste Bartholdi, built it from copper, giving the statue a warm penny-colored hue. The reason behind its transformation is pretty wild.

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Over time, the then-iconic shade faded due to natural weather conditions and simple aging. The craziest part is that by the time color photography had been invented, Lady Liberty was already the hue it is today—we have no true records of its original appearance.

8. Believe it or not, Brooklyn almost wasn’t even a part of New York City at all. In the 1890s, residents of the iconic borough were not yet consolidated with the rest of the city — and due to concerns over taxes and maintaining their independence, many didn’t want to be.

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It was an intense battle between those for and against consolidation, and when voting day came the results were so close that had the anti-consolidationists won, the city as we know it today would be completely altered. Thankfully, a mere 278 people swung the vote in favor of keeping Brooklyn.

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9. In New York City, ethnic enclaves abound. From Chinatown to Little India, there are a plethora of culturally diverse neighborhoods. But few realize that one well-known area of the city actually used to be its own “Little Germany.”

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During the mid-1800s, the Lower East Side was flooded with German immigrants. But most residents fled following the fiery Slocum Disaster on the East River. They were replaced by a predominately Jewish community who maintain a huge presence there to this day. You never know what you’ll see in the Big Apple…

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10. In December of 1960, two commercial planes tragically collided mid-air. One of them crash-landed in Staten Island, and the other right in the center of the now picture-perfect Park Slope. Six pedestrians and all passengers were killed. But the saddest part?

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To this day, no official memorial or plaque for these victims has been placed in the neighborhood. The only sign that anything ever went awry is discolored bricks on a nearby building — the previous ones had to be replaced due to damage from the crash.