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

Blockbuster

During the 1980s and 1990s, Friday night often meant one thing for American families: a trip to Blockbuster. Browsing the aisles for a movie, debating what to watch, and grabbing popcorn at the counter became a weekly routine. But nothing lasts forever.

Born in 1985, Blockbuster conquered the massive home-video market with thousands of stores by the late 1990s and early 2000s, catering to families with at-home VCRs. Then technology changed everything. First came DVD-by-mail services like Netflix, followed by streaming, which left Blockbuster struggling. Late fees and inconvenience only pushed more customers away. The company filed for bankruptcy in 2010. Today, just one official store remains in Bend, Oregon, where visitors still stop by for a dose of the video-store era.

2

Kodak

Back in the day, almost every vacation, birthday, wedding, or holiday gathering seemed to include a Kodak camera, or at least a roll of Kodak film. Founded in 1881, Kodak helped keep the moments that filled family photo albums for generations.

From the 1960s through the 1990s, Kodak dominated the world of film and photography. But that success also made the company slow to accept that technology was changing. Ironically, Kodak helped invent one of the first digital cameras in 1975, yet it hesitated to embrace the future. By the 1990s and 2000s, digital cameras (and later camera phones) quickly replaced traditional film. In 2012, the company declared bankruptcy.

3

Pan Am

Long before flying became an everyday experience, Pan American World Airways, better known as Pan Am, was already carrying Americans across the world. It was founded in 1927, and during the 1960s and 1970s, the airline became a symbol of glamorous air travel.

Its famous blue globe logo was instantly recognizable, even to those who rarely flew. But by the late 1970s, rising competition, fuel costs, and financial troubles began weakening the company. After years of mounting losses and debt, Pan Am shut down in 1991. Even so, its fame was such that even today, more than 30 years later, we still remember it.

4

Woolworth’s

Before Woolworth's made the "five-and-dime" famous, shopping in America looked very different. For decades, Americans visited Woolworth’s for everything from toys and school supplies to household goods and everyday essentials. By the 1960s, the brand had become a familiar part of American life.

Created in 1879 by Frank Winfield Woolworth, the chain grew into one of the country’s largest retailers. But in the 1970s, malls and discount giants like Walmart changed the way Americans shopped, and Woolworth struggled to keep up. By the 1980s, the iconic chain was slowly disappearing. Most stores closed during the 1990s, and the Woolworth retail chain officially ended in 1997.

5

Circuit City

Testing giant stereo systems, browsing rows of CDs and video games, and shopping for the newest TV were all part of the experience at Circuit City, once one of America’s biggest electronics chains.

Founded in 1949 by Samuel S. Wurtzel in Richmond, Virginia, as "Wards Company," the retailer adopted the Circuit City name in 1984. During the 1980s, 1990s, and early 2000s, it became the go-to place for Americans buying a TV, stereo, computer, or any electronic device. But like many companies on this list, Circuit City struggled as shopping habits changed and online stores became more convenient. A controversial 2007 decision to lay off thousands of experienced employees further hurt the company’s reputation. Circuit City couldn’t survive mounting losses and closed all remaining stores in 2009.

6

Borders

Remember Borders? Born in 1971, its huge stores, filled with books, music, magazines, and cozy reading spaces, invited customers to spend entire afternoons there.

During the 1990s and early 2000s, the rise of large shopping malls actually helped Borders thrive, turning its bookstores into popular destinations inside malls across the US. But eventually, the company ran into a challenge it couldn’t overcome: online shopping and digital reading. Competitors like Amazon surged ahead, while Borders struggled to adapt and made costly business decisions, including outsourcing its online sales to Amazon for years. The company collapsed financially in 2011 and soon closed all remaining stores.

7

Bugle Boy

In the late 1980s and early 1990s, teenage fashion became almost synonymous with Bugle Boy. Famous across the country for its casual jeans and memorable TV commercials, the brand became a major part of American mall culture and was sold in department stores nationwide.

But fashion never stands still, and brands have to constantly adapt to survive. By the late 1990s, newer youth-oriented labels had taken over with fresh styles that quickly made Bugle Boy seem outdated. Sales began to fall, and after years of struggling to keep up with changing trends, the company closed its stores in 2001.

8

Howard Johnson’s restaurants

During the 1960s and 1970s, a stop at Howard Johnson's was part of the classic American road-trip experience for many families, and that was no accident.

Founded in 1925 in Quincy, Massachusetts, the famous orange-roofed chain reached its peak when America’s expanding highways and booming car culture made roadside travel more popular than ever. But by the late 1970s and early 1980s, the growing popularity of fast-food chains like McDonald's began changing the way Americans ate on the road. Drivers increasingly wanted meals that were faster, cheaper, and more standardized, while interstate highways also redirected traffic away from many older roadside locations. Unlike some other brands on this list, Howard Johnson’s faded away slowly over the decades. The last restaurant finally closed in 2022.

9

Burger Chef

In 1958, a name emerged as one of the pioneers of America’s growing fast-food industry: Burger Chef. By the late 1960s, the chain had more than 1,000 locations across the country and had become one of McDonald's’s biggest competitors.

Long before Happy Meals became famous, Burger Chef helped popularize the idea of marketing meals directly to children with toys and themed publicity. But during the fast-food wars of the 1970s, competition became fiercer than ever. While McDonald’s and Burger King expanded by leaps and bounds, Burger Chef struggled with financial problems and changing consumer tastes. In 1982, the company was sold to Hardee's, which gradually converted most Burger Chef locations into Hardee’s restaurants.

10

Sports Authority

Throughout the 1990s and 2000s, many Americans looking for running shoes, gym shorts, and sports gear headed straight to Sports Authority.

Known for its huge stores packed with athletic apparel, exercise equipment, bicycles, camping gear, and team sports products, Sports Authority became the ideal shopping destination for families and athletes across the US. But as online shopping rapidly changed retail in the 2000s, the company struggled to adapt. Heavy debt from expansion efforts and a slow shift to e-commerce eventually caught up with the chain. Sports Authority declared bankruptcy in 2016 and closed all remaining stores later that year.

1

What are bills made of?

Unlike other currencies, dollar bills are not made of paper or plastic. U.S. dollar bills are made from a special fabric blend composed of 75% cotton and 25% linen. This mix makes the bills extremely durable and resistant, and they can be folded about 4000 times before tearing.

2

What bills are valid?

Any U.S. dollar bill that was legally printed is valid, no matter how old, as American currency does not have an expiration date. While some bills might not be accepted by businesses of foreign exchange services due to their condition or if they are a discontinued version of the bill, the bills themselves are still valid, and American banks will accept them, though they might take them out of circulation.

3

American leaders

Five bills have a depiction of an American president. The exceptions are the $10 bill, with Alexander Hamilton on the front, and the $100 bill, with Benjamin Franklin. The $1 bill, depicting George Washington, is extremely symbolic: several elements are repeated 13 times as a nod to the thirteen colonies, and it showcases the Bald Eagle and the Eye of Providence as a sign of God watching over America.

4

A change in size

Did you know that dollar bills used to be so big that they were nicknamed "horse blankets"? Original dollar bills were 7.4 × 3.1 inches. In 1929, the Treasury Department reduced the size of bills to 6.14 × 2.61 inches to reduce production costs and materials. Old bills, though still valid, are worth much more as collector items.

5

Uniformity

Besides their value and design, all dollar bills have the same size (6.14 × 2.61 inches), color, and weight (1 gram) , which sets American currency apart from other countries where bills of different values are differentiated by size, color, or both. Why doesn’t the U.S. implement differences among bills? The cost of adapting vending machines, bank drawers, and ATMs to new bill sizes would cost billions of dollars.

6

Hard to copy

Originally, dollars were not green, but black. As time passed, green ink was favored, as it was cheap and did not fade as much as black. The new color also prevented people from using black-and-white cameras to create counterfeit money. Currently, dollar bills are predominantly green, but newer versions also include extra colors, such as pink, orange, or purple.

7

A $100,000 bill?

Have you ever seen a $500 or 1,000 dollar bill? What about a $100,000? Up until 1945, the U.S. Treasury printed $500, $1,000, $5,000, $10,000, and $100,000 notes , in addition to the values currently in use. These higher-value notes were mainly intended for bank and government use, but were sought by criminals as they made it easier to hide large amounts of money. Even though they were officially discontinued in 1969, these notes are still valid, though rare, and they have a high worth as collector's items.

8

No numbers

Unlike bills, American coins have different sizes and colors related to their value. Originally, gold, silver, and copper were used for coins, but modern coins are made of copper, zinc, or nickel. Besides their size and design, the value of each coin is printed in letters, not in numbers , alongside depictions of American presidents.

9

Liberty for all (the coins)

By law, all American coins must include six specific details : the word ‘Liberty’, the name of our country, the national motto "In God We Trust", the oldest American motto "E Pluribus Unum", the value of the coin, and the year. Each coin also includes a mint mark that shows where it was made: "P" for Philadelphia, "D" for Denver, "S" for San Francisco, and "W" for West Point.

10

A global currency

The American dollar is one of the most powerful currencies in the world, acting as a backbone for international trade and finances. It is estimated that two-thirds of the physical dollars in circulation are outside American territory. Besides the U.S. and its territories, eight sovereign nations have the U.S. dollar as their official currency, with several more accepting it as legal tender.