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.

1

Area 51

Image: Michael Herren

Location: Nevada

Shrouded in secrecy, this military base has become synonymous with UFOs and government cover-ups. Its official purpose was testing aircraft like the U-2 spy plane and Stealth Bomber, but its classified nature fueled decades of wild speculation, ranging from secret weapons to actual aliens working for the government.

2

Coral Castle

Image: Audric Wonkam

Location: Florida

This massive stone structure was built by a single man, Edward Leedskalnin, using enormous limestone blocks—some weighing 30 tons. According to him, no heavy machinery was ever used during the construction, and he even claimed to know the secrets of the pyramids . To this day, engineers and historians debate how he moved and placed those stones with such precision.

3

Skinwalker Ranch

Image: Jacob Padilla

Location: Utah

This 512-acre property has long been at the center of UFO sightings, cattle mutilations , and alleged portals to other dimensions. The stories were so compelling that, in the ’90s, a private research organization purchased the ranch to try and make some scientific sense of the claims, conducting extensive field studies. However, after nearly a decade of research, they found no conclusive evidence.

4

Mammoth Cave

Image: Ksenia Kudelkina

Location: Kentucky

The world’s longest known cave system has its fair share of unexplored tunnels, ghost stories, and strange air currents. More than 400 miles have been mapped , yet many passages remain uncharted. Researchers have yet to fully understand the cave’s underground ecosystem, and new chambers are still being discovered today.

5

The Marfa Lights

Image: Alexandra Vo

Location: Texas

Reported since at least the late 19th century, floating orbs of light have been seen near this small town with no consistent explanation. Night watchers continue to gather at designated viewing areas along Highway 90, hoping for a glimpse. While scientific studies suggest that distorted car headlights are the most likely cause, many remain convinced otherwise.

6

The Devil’s Kettle

Image: Andrew Ling

Location: Minnesota

This unusual waterfall splits in two—one half flows normally, while the other vanishes into a deep pothole with no known exit. Scientists poured dye, ping-pong balls, and even GPS trackers into the mysterious hole, all to see where the water ends up. While researchers eventually confirmed it rejoins the river underground, exactly how and where remained elusive for decades.

7

Cahokia Mounds

Image: pcrm Dorego

Location: Illinois

Built centuries before Columbus arrived in the Americas, the ancient city of Cahokia featured massive earthen mounds, wooden palisades, and likely formed part of complex trade networks across the continent. Despite having a population rivaling London in the 1200s, according to archaeologists, the city was mysteriously abandoned in the span of a few years. No written records explain its decline, though environmental stress, resource shortages, and internal social factors are often cited as possible causes.

8

Blythe Intaglios

Image: Alexander Schimmeck

Location: California

Similar to Peru’s Nazca Lines, these giant geoglyphs are etched into the desert floor, seemingly visible only from the sky. Created by scraping away dark rocks to reveal lighter earth beneath, the figures are believed to be between 450 and 2,000 years old, depending on the specific design. While their exact purpose remains a mystery, they are believed to have had a ceremonial function.

9

The Spooklight

Image: Ben Griffiths

Location: Missouri-Oklahoma Border

Also known as the Hornet Spooklight, this floating orb has been seen since at least the late 19th century. It appears along a rural stretch of road near the small community of Hornet, Missouri, and Quapaw, Oklahoma. While some theorize it could be caused by car lights from miles away, some sightings predate automobiles.

10

Roanoke Island

Image: Stephen Crane

Location: North Carolina

In the 1580s, an entire colony vanished overnight, leaving behind only the word "Croatoan" carved into a tree. No graves, no remains—just an eerie disappearance that sparked centuries of theories, from disease and starvation to assimilation with local tribes. Modern archaeology uncovered European artifacts at sites associated with Native groups miles away, but no definitive evidence has ever solved the mystery.

1

How the White House gained its name

Originally, the building was called the "President’s House." That only changed after the 1814 fire. During the War of 1812, British troops marched into Washington and set many buildings on fire, including the main one.

Walls were scorched, and smoke damage lingered inside and outside the building. When repairs began, painters coated the building white to cover the burn marks . This resulted in the "White House" nickname. Nearly a century later, Theodore Roosevelt made it official.

2

A hidden underground beneath America’s books

Have you ever heard of the Library of Congress's underground tunnels? Most visitors never see them or learn about them. They connect their buildings, allowing staff to transport rare books and documents safely and efficiently. Fragile, valuable materials had better be protected from the weather, the sunlight, and, well, the people!

3

The Golden Gate Bridge wasn’t supposed to stay red

The reddish color of the Golden Gate Bridge (officially named "International Orange") was supposed to be a temporary priming coat to protect the steel.

However, when engineers looked at the bright color peeking through the fog against the stunning blue and green of the San Francisco Bay, they said, "You know what?" It should stay like that. The Navy proposed painting it black and yellow, but it was never done. The stunning color turned it into one of the most iconic buildings in the world.

4

The Empire State Building wanted to welcome airships

Back in 1931, the Empire State Building’s spire was intended as a mooring mast to serve as a docking station for airships. The idea was that passengers should be able to step directly into Manhattan from the sky!

Sure, it was a futuristic plan, but it was eventually dismissed for being wildly dangerous. Passengers would have had to climb out at dizzying heights in strong winds. Not ideal! And certainly not glamorous.

5

The famous ceiling that got the stars wrong

You may have seen images of Grand Central Terminal’s celestial ceiling —or seen it with your own eyes. But there’s a twist: Did you know that the constellations in it are painted backward?

The way they are represented is as if viewed from outside the universe, rather than from Earth. Whether it was a mistake by the artist or it was an intentional reverse on cosmic perspective, the terminal ceiling has looked like this since its opening in 1913.

6

The president who quietly ran a whiskey empire

George Washington is remembered as a general and a president, of course. But he was also a major whiskey producer. Hidden on the grounds of Mount Vernon was a fully functioning distillery, built in the late 1790s.

By the time of Washington’s death, it was producing nearly 11,000 gallons of whiskey a year. That made him one of the largest distillers in the young United States!

7

The iconic façade didn’t exist during the battle

When you think of the Alamo, you surely picture its iconic façade. However, that structure was not part of the original mission!

During the famous 1836 battle, the building looked far simpler, and it lacked its now-famous curved top. That façade was added decades later by the U.S. Army when the structure was used as a supply depot

8

Why visitors can no longer climb to the torch

Did you ever hear some old relative’s anecdote ot climbing all the way to the top of Lady Liberty’s torch? They weren’t lying: Up until 1916, visitors could. However, around that time, some explosions in a nearby munitions depot sent shockwaves through the statue.

The blast damaged the torch and weakened its structure. For safety reasons, access was permanently closed to the public.

9

The concrete that is still hardening today

The Hoover Dam contains so much concrete that it generates heat as it cures. Engineers knew that if poured as one solid mass, it would take more than a century to cool and could crack.

Instead, they built it using interlocking concrete blocks, each cooled with circulating water. Even so, parts of the dam are still slowly curing today.

10

The building that accidentally cooked its neighbors

When the Walt Disney Concert Hall opened in Los Angeles, its gleaming metal exterior stunned visitors. But it also caused an unexpected problem…

The highly reflective steel panels bounced sunlight onto nearby sidewalks and apartments. In some spots, the glare was so intense that it melted materials! As a result, engineers eventually had to dull parts of the surface.

11

The Capitol’s dome isn’t stone

The grand, massive dome atop the U.S. Capitol looks like solid stone, doesn’t it? But, in fact, it is made of cast iron.

In the mid-1800s, stone was considered too heavy and expensive for such an ambitious structure. Cast iron allowed builders to create a taller, more ornate dome that weighs nearly nine million pounds.