1

A renovation project saved thousands of lives on 9/11

On September 11, 2001, American Airlines Flight 77 struck the Pentagon at 9:37 a.m., killing 189 people. Few people know this part: the death toll could have been much higher. But there was a renovation project underway at the time of the attacks.

The Pentagon’s five-sided structure is divided into five "wedges," and workers had been renovating them one at a time. Flight 77 struck the wedge that had just been completed. Of the 4,500 people who normally worked in that section, only about 800 had moved back in. Without the reinforced construction and the incomplete occupancy, experts believe the casualties would have been catastrophically higher.

2

The Cold War and the hot dog stand

In the middle of the Pentagon’s five-acre center courtyard once stood a modest hot dog stand. According to a Cold War legend (one still retold by official Pentagon tour guides on every public tour), between the 60s and the 80s, Soviet satellite images tracked large groups of high-ranking military officials converging on that small building at the same time every day.

Soviet intelligence reportedly concluded the structure must be the entrance to some underground bunker in America. In reality, all it did was sell lunch. In 2006, the original stand was torn down, and a sandwich shop was built in its place.

3

Its construction began on September 11th, exactly 60 years before the attack

Builders broke ground on the Pentagon on September 11, 1941. That was exactly 60 years to the day before the September 11, 2001, terrorist attacks that would strike the same building.

Construction had been ordered by Army Brigadier General Brehon Somervell, who wanted a permanent headquarters for the Defense Department to replace its then-17 scattered offices across Washington, D.C.

The project was extraordinarily ambitious: plans called for the world’s largest office building to be completed in just 16 months. In the end, the conception, design, and construction of the entire Pentagon building took a total of 15 months.

4

The same person oversaw its construction and the Manhattan Project

Colonel Leslie Groves of the Army Corps of Engineers took charge of Pentagon construction in August 1941. He worked six days a week and drove his team relentlessly, at one point employing more than 15,000 workers around the clock.

When the Pentagon was finished in January 1943, Groves was assigned to lead the Manhattan Project, America’s secret program to build the atomic bomb . His deputy, Captain Robert Furman, followed him into the Manhattan Project as chief of foreign intelligence. Together, the men who built the world’s largest office building went on to produce the weapon that ended World War II.

5

Why is it shaped like that?

The Pentagon’s iconic five-sided shape was the consequence of a geographic accident. The original site selected for the building, near Arlington Cemetery, **happened to be bordered on five sides by roads. **Architects designed the structure to fit those boundaries, producing a pentagonal floor plan. Then President Franklin D. Roosevelt intervened: worried the massive building would obstruct the view of Washington, D.C. from Arlington, he ordered the site moved to its current location along the Potomac River. But the five-sided design had already been drawn up, and nobody changed it.

6

It was the first desegregated building in Virginia

When the Pentagon was designed in 1941, segregation was the law in Virginia. Original plans called for doubled bathroom facilities: separate ones for Black and white employees, as required by Virginia statute. But President Roosevelt had signed Executive Order 8802 in June 1941, prohibiting racial discrimination in federal employment and government contracting.

As a federal building, the Pentagon was exempt from Virginia law. It became the only building in the state where segregation was not enforced. A fully desegregated federal workplace that opened in 1943. The doubled bathrooms were built anyway, as the plans were too far along to revise, but were never used as separately designated spaces.

7

Its construction was surprisingly frugal and incredibly fast

Ground broke on September 11, 1941, and construction finished on January 15, 1943, just 16 months later. More than 15,000 workers were on site around the clock. Wartime office shortages were so severe that employees moved into completed wings before the rest of the building was finished. Steel was too scarce to use extensively, so builders relied almost entirely on reinforced concrete. The 689,000 tons of sand and gravel required came directly from the nearby Potomac River, cutting transportation costs. The project was budgeted at $35 million, but the final bill was $63 million, which would translate to over $900 million in today’s dollars.

8

You can walk between its farthest points in only 7 minutes

The Pentagon is the world’s largest low-rise office building: 6.5 million square feet of space, which is three times the total floor area of the Empire State Building. Each of its five outer walls is 921 feet long. It has 7,754 windows and 17.5 miles of corridors. Approximately 26,000 military and civilian employees report for work there every day.

Despite that scale, the building’s concentric ring design is so efficient that it takes only about seven minutes to walk between its two farthest points.

9

The man who secretly lived inside its walls

During construction, Colonel Groves drove his deputy, Captain Robert Furman, so relentlessly that Furman rarely left the building. To cope, Furman had contractors build him a small, windowless apartment hidden inside the walls of the Army’s Ordnance Division. In this private room, he could sleep and shower without leaving the premises.

When construction ended and personnel dispersed, knowledge of the hidden room was never passed on to building management. Months later, when Furman returned to Washington on Manhattan Project intelligence business, he found the apartment undiscovered and exactly as he’d left it.

For over a year, he would slip back to the Pentagon, pop open a wall panel, spend the night, and emerge in the morning with his suitcase. He was finally caught in 1943 and forced to surrender the keys. It was never disclosed whether the secret apartment was maintained or eventually absorbed back into the official floor plans.

10

It houses over 30 restaurants, including everyone's favorite chains

The Pentagon feeds roughly 26,000 people a day, and its dining options read less like a military headquarters and more like a mall food court. The main Concourse Food Court, which opened in September 2009 and seats 875 people, is the largest of several dining areas.

Confirmed chains currently inside the building include McDonald’s, Five Guys, Subway, Popeyes, Starbucks (multiple locations), Dunkin’ (two locations), Panera Bread, Taco Bell, Panda Express, Baskin-Robbins, Potbelly, Jamba Juice, and Moe’s Southwest Grill, among others. The building also houses a CVS pharmacy, a florist, a jeweler, and a dry cleaner. In the summer of 2024, Potbelly became the first restaurant to open in the center courtyard. Yes, the very spot where the legendary Cold War hot dog stand once stood.

1

Bill Clinton

Have you heard of Bill Blythe? Probably not, but you definitely know who he is: Bill Clinton, the 42nd president of the United States.

Born William Jefferson Blythe III on August 19, 1946, in Hope, Arkansas, Clinton never knew his biological father, who passed away in a car accident three months before he was born. His mother, Virginia Cassidy Blythe, later married Roger Clinton Sr. At 15 years old, Bill chose to take the surname Clinton, adopting the name of the man who had raised him .

2

Lyndon B. Johnson

Have you ever heard of a baby who went three months without a name ? As unusual as it sounds, one US president began life exactly that way.

The future Lyndon B. Johnson was born on August 27, 1908, near Stonewall, Texas. But instead of naming their newborn son, his parents found themselves in a standoff. According to historical records from the Miller Center at the University of Virginia, his mother, Rebekah Baines Johnson, wanted to name him Clarence, while his father, Sam Ealy Johnson, wanted the baby named after himself. Unable to agree, they left him officially unnamed, and for the first three months of his life, he was simply "Baby Boy Johnson." The deadlock finally ended when his mother gave in, and the future president was named Lyndon Baines Johnson , honoring Lyndon Baines, a family friend admired by his father.

3

Ulysses S. Grant

The 18th president of the United States wasn't born with the name we all know. He was born on April 27, 1822, in Point Pleasant, Ohio, as Hiram Ulysses Grant. So where did the famous "S." come from?

The answer is a paperwork mistake. In 1839, Ohio Congressman Thomas Hamer nominated the 17-year-old Grant to the US Military Academy at West Point. Knowing the young man went by Ulysses and that his mother's maiden name was Simpson, Hamer accidentally wrote "Ulysses S. Grant" on the nomination. Grant considered correcting the error, but eventually gave up, for two main reasons. He disliked the initials of his birth name, "H.U.G.", so the mistake didn't bother him much. In addition, fixing it would have meant a mountain of paperwork that could have jeopardized his appointment to West Point. So he simply let the new name stand, and the accidental middle initial stayed with him for the rest of his life.

4

Harry S. Truman

Harry S. Truman may have one of the strangest stories on this list.

His first name, Harry, honored his maternal uncle, Harrison "Harry" Young. His middle initial, however, didn't actually stand for anything. Truman's parents chose the "S" to honor both of his grandfathers, Anderson Shipp Truman and Solomon Young, without choosing one name over the other. In other words, the "S" wasn't short for Shipp or Solomon; it was simply "S". Truman himself usually wrote it without a period, since it wasn't an abbreviation. But after he became president, his staff encouraged him to add the period in official correspondence because it looked more conventional. That's why today he's almost always remembered as Harry S. Truman.

5

Dwight D. Eisenhower

President Dwight D. Eisenhower is remembered for leading the nation through the Cold War and signing the Civil Rights Act of 1957. But there's one surprising detail about him that most people never hear.

The man we know as Dwight Eisenhower was actually born David Dwight Eisenhower on October 14, 1890, in Denison, Texas. Named after his father, David Jacob Eisenhower, he quickly ended up with a problem: there were now two Davids in the same household. To avoid the confusion, his mother, Ida, simply began calling her son Dwight instead. He went by his middle name as if it were his first for years, but the change didn't become official until he applied to West Point at age 20. Wanting his official records to match the name everyone already knew him by, he registered as Dwight David Eisenhower and made the switch permanent.

6

Gerald R. Ford

On July 14, 1913, a baby boy named Leslie Lynch King Jr. was born in Omaha, Nebraska, and 61 years later, he became the 38th president of the United States. If the name doesn't sound familiar, there's a good reason: he entered the White House under a completely different name.

Leslie Lynch King Jr. was named after his father. However, just 16 days after his birth, his mother, Dorothy, fled the marriage with her infant son to escape her abusive husband. Three years later, she divorced King and married Gerald Rudolph Ford, a paint salesman who raised the boy as his own. From then on, everyone knew him as Gerald Rudolph Ford Jr. , even though he didn't legally change his name until December 3, 1935, when he was 22 years old.

7

Ronald Reagan

Have you ever heard of "Dutch" Reagan? Perhaps not, but that was in fact the childhood nickname of Ronald Reagan, the 40th president of the United States.

Born as Ronald Wilson Reagan on February 6, 1911, in Tampico, Illinois, Reagan got his nickname from his father, who thought his newborn son looked like a "fat little Dutchman." The moniker stuck almost immediately. As a boy, Reagan embraced it so completely that, according to his autobiographies and records at the Ronald Reagan Presidential Library, he disliked being called Ronald and insisted everyone call him Dutch instead. That changed only after he arrived in Hollywood in the late 1930s, when studio executives convinced him that "Dutch Reagan" wasn't exactly leading-man material.

8

Jimmy Carter

Born James Earl Carter Jr. on October 1, 1924, in Plains, Georgia, and named after his father, the future president had been called "Jimmy" almost from the day he was born.

Over the years, the nickname became the name he truly identified with. So when he took the presidential oath in 1977, Carter broke with tradition. Instead of using his formal first name like all the presidents, he was sworn in as Jimmy Carter, becoming the first (and still the only) US president to take the oath of office using a nickname rather than his legal name.

9

John Quincy Adams

The second president of the United States, John Adams, is one of the best-known Founding Fathers. His name is instantly recognizable to most Americans, and that's exactly why his son made an important decision about what he would be called.

John Quincy Adams was born on July 11, 1767, in the North Precinct of Braintree, Massachusetts, an area that was officially renamed Quincy in 1792. The nation's sixth president and the first son of a president to become president himself carried a name with a story. He was named not only after his father, but also after his maternal great-grandfather, Colonel John Quincy, who was gravely ill when the baby was born. Although Quincy was originally a family surname, it became the baby’s middle name. As an adult, he embraced all three names, John Quincy Adams, helping distinguish himself from his famous father while honoring both sides of his family.

10

Grover Cleveland

Most people have never heard of Stephen Cleveland, but mention Grover Cleveland, and they'll know exactly who you're talking about. The thing is, they're the same person.

Born on March 18, 1837, in Caldwell, New Jersey, the future 22nd and 24th president of the United States was actually named Stephen Grover Cleveland. His father, a Presbyterian minister, chose the name to honor Reverend Stephen Grover, the first pastor of the First Presbyterian Church in Caldwell, where he was serving at the time. As he grew older, however, Cleveland made an unusual choice: instead of going by his first name, Stephen, he adopted his middle name because he simply liked the sound of "Grover Cleveland" better.

1

Raven Rock Mountain Complex

Image: Ilagam

Did you know that in the 1950s, the US government carved out a secret underground city that could survive a nuclear attack? It’s called an "underground Pentagon", and very much like Area 51, it is one of the government's most classified projects.

This military complex and nuclear bunker is located near Blue Ridge Summit, Pennsylvania, 768 feet below the ground. It’s protected by 23.5 ft thick 30-ton doors built on top of springs to survive the shock from a blast. Raven Rock has five buildings with 15 floors big enough to live and work. The base has everything it needs to keep running, like a cafeteria, a barbershop, water generators, and even a medical center.

2

SubTropolis

Image: mwewering

Below Kansas City, Missouri, lies the world's largest underground business complex. SubTropolis is a structure located inside a mine north of the Missouri River. It was carved out of limestone some 135 to 185 feet underground and covers a total of 55 million square feet.

Kansas City Chiefs founder Lamar Hunt built this subterranean city in the 1960s. It has offices, storage space, and even factories. Over 1,600 people work here every day, largely because SubTropolis remains cool all year, making it an ideal location for businesses. Fun fact: some of Hollywood’s most beloved masterpieces are kept here, including the original film reels of Gone with the Wind and The Wizard of Oz.

3

Underground Atlanta

Image: Ronny Sison

Underground Atlanta is a historic spot in downtown Atlanta, Georgia. It was built in the late 1800s, right after the Civil War, as a commercial district centered around the railroad. In the 1920s, viaducts were built and the streets were raised, creating a second level of streets, buildings, and shops.

During Prohibition, the abandoned underground space served as the best spot for speakeasies and juke joints. For decades, people forgot about the hidden city, but in the 1960s, it was brought back to life as a fun place for music bars and nightlife.

4

New York City Subterranean World

Image: Photographer: unknown, Public domain, via Wikimedia Commons

Under America’s most populous city, there's a whole hidden world. For example, beneath Little Italy and the Public Library, there are secret vaults. Beyond the subway millions of people use daily, there is City Hall station, opened in 1904 and closed in 1945. It's a hidden gem with stained glass and mosaics that you can still visit by staying on the 6 train past the last stop.

But that’s not all! There are trading tunnels in SoHo and old cattle tunnels in the Meatpacking District. Also, in 1897, there were mail tubes built around the city to send letters between post offices that operated until the 1950s. Some of these underground spaces go as deep as 800 feet!

5

Permafrost Tunnel Research Facility

Image: Paxson Woelber

A large part of the land in the northern hemisphere is Permafrost, so it makes sense that there is a research facility specially built to study it. The Permafrost Tunnel in Alaska is the best place to learn about frozen soil that's over 40,000 years old.

The long tunnel was dug from 1963 to 1969 to study how to build and mine in frozen environments. Inside the facility, scientists study ice, ancient plants, and even bones from animals like mammoths. The tunnel shows different layers of earth, uncovering frozen ground from different time periods that help scientists anticipate what might happen as the world gets warmer.

6

The Greenbrier Bunker

Image: Alex Holzreiter

The Greenbrier Bunker in White Sulphur Springs, West Virginia, is a secret underground facility beneath a luxury hotel that has hosted numerous US presidents and famous guests. It was built during the Cold War to protect the US Congress in the event of a nuclear attack. The bunker was designed to house all 535 members of Congress and their staff for a long time.

This classified underground facility remained a secret until 1992, when a Washington Post article exposed it. Today, visitors can take tours to see special rooms, blast doors, and decontamination areas.

7

The Caverns

Image: jymy duhomme

Would you attend a concert underground? If you travel to Tennessee is totally possible! The Caverns, formerly known as Bluegrass Underground, is a very cool spot in Grundy County, Tennessee. Lying deep in a cave 333 feet underground, this concert venue with natural acoustics is the perfect place for live music.

People come from all over to hear a variety of performances, especially Bluegrass music. The Caverns can accommodate up to 1,200 people standing up and are equipped with state-of-the-art sound and lights. The cave's cool and quiet atmosphere makes the experience extra special!

8

Crystal City Underground

Image: Gustavo Alejandro Espinosa Reyes

Beneath the neighborhood of Crystal City, near Washington, DC, lies a network of shops, restaurants, and offices. It opened in 1976 and was designed to feel like an old shopping village with cobblestone streets and antique glass windows.

The underground space covers 150,000 square feet and connects several buildings. It's a popular spot for office workers and visitors, especially when the weather is bad. Unfortunately, in 2024, the shops closed, ending their retail era. Yet, the underground walkways and connections to the Metro remain open for pedestrians.

9

Los Angeles Prohibition Tunnels

Image: Alpha Perspective

In the 1920s, during Prohibition, people had to find ingenious ways around the restrictions on selling and consuming alcohol. That's why they built about 11 miles of underground tunnels right under Los Angeles.

Many of these subterranean sites are now closed, but you can still find a few hidden entrances around the city. You can even go on a tour to explore the tunnels and learn about their secret history.

10

Havre Beneath the Streets

Image: Đào Việt Hoàng

After a big fire in 1904 destroyed Havre’s business district in Montana, many shops moved underground. They used the old steam tunnels to stay safe from fires and bad weather. For years, the tunnels were busy with people and stores, such as saloons, drugstores, laundromats, and even a brothel. But today it is completely silent.

Fortunately, you can still visit what is left of this hidden city to see old shops and learn how people stayed safe and worked over 100 years ago. It's like going back in time!

11

Cheyenne Mountain Complex

Image: See page for author, Public domain, via Wikimedia Commons

One of the safest places in the world is right here in America, more specifically in El Paso County, Colorado. Hidden inside a mountain, Cheyenne Mountain Complex was built in the 1960s to protect the US military from nuclear attacks.

The bunker stands under 2,000 feet of solid Granite, making it super strong and safe. It was once the command center for NORAD (North American Aerospace Defense Command). The complex has blast doors that weigh 25 tons each and can withstand a nuclear blast. It also has its own power, water, and food supply. People could survive there for months!

12

Forestiere Underground Gardens

Image: Levi Clancy, CC0, via Wikimedia Commons

A Sicilian immigrant called Baldassare Forestiere spent 40 years digging and building a series of subterranean structures by hand in Fresno, California. Inspired by Roman catacombs and old wine cellars, he created around 65 rooms, tunnels, and courtyards to escape the hot summer sun.

The Gardens have fruit trees, grapevines, fishponds, and even a chapel. Some of the trees are more than 90 years old! Today, Forestiere Underground Gardens is a Historical Landmark you can visit if you want to discover a true underground paradise.