1

Seattle Underground City

Did you know the remnants of Seattle's original streets are still accessible? Beneath the bustling streets of modern-day Seattle lies the Underground City , a network of subterranean passageways that formed the ground level in the 1800s.

By the end of the 19th century, after the Great Seattle Fire, it was decided to rebuild the city at a higher elevation to combat frequent flooding . So, these original streets, sidewalks, and storefronts were buried, and with it, much of their history.

Guided tours take people through tunnels and ladders and retell real and eerie stories about the history of the Underground City.

2

Luray Caverns

Image: Robert Thiemann

Have you ever heard of the underground Stalacpipe Organ ? Not only is it a one-of-a-kind interaction between keyboards and cavern stalactites, but it is also the largest musical instrument in the world, according to Guinness World Records.

This instrument lives in the Luray Caverns, Virginia. It consists of an electric console that taps on these ancient stalactites of varying sizes to produce musical tones. A subterranean wonder, these caverns are also known for their extraordinary size , housing towering stalactites and stalagmites, mirrored pools, and delicate drapery-like calcite formations.

3

The Underground Gardens of Baldassare Forestiere

Image: Adrian Botica

This stunning subterranean retreat was built entirely by hand. Tucked under the sun-scorched landscape of Fresno, California, lie the Underground Gardens of Baldassare Forestiere . They are the life’s work of Baldassare Forestiere, a Sicilian immigrant who started digging in the early 1900s to escape the Central Valley's oppressive heat.

Over 40 years, drawing inspiration from ancient Roman catacombs , Forestiere carved an elaborate network of underground rooms, passageways, grottoes, and courtyards that span 10 acres.

A unique masterpiece, the gardens are open with guided tours that lead guests through beautifully designed spaces featuring skylights, arches, and alcoves. This oasis also boasts an array of fruit trees, including citrus, figs, and olives.

4

Ruby Falls

Image: Goodfreephotos_com

Colorful and breathtaking, the Ruby Falls is a geological wonder located inside Lookout Mountain near Chattanooga, Tennessee.

Hidden over 1,000 feet below the mountain's surface, this waterfall cascades 145 feet into a pool , making it one of the tallest underground waterfalls open to the public.

Visitors enter the mountain and descend via elevator. Then, they walk through stunning cave formations such as stalactites, stalagmites, and flowstone. At the waterfall chamber, multicolored lights –powered by renewable energy– illuminate the falls. Lantern-lit tours are also offered as a chance to visit the marvel with a different charm.

5

The Catacombs of Green-Wood Cemetery

Image: Joy Ernst

Arched tunnels of tranquil, sacred vaults lie beneath the Green-Wood Cemetery in Brooklyn, New York. Built in the mid-19th century, these catacombs were designed as a prestigious resting place for the city’s elite , prominent families.

While the catacombs are typically closed to the public, special events are sometimes organized to welcome visitors, such as art expositions, guided history tours, and candlelit tours seasoned with live music and storytelling.

Outside, where the sun does reach, await the serene landscapes and remarkable monuments of the cemetery, which is itself a National Historic Landmark .

6

The Lost Sea

Image: Roberto Nickson

The largest underground lake in America is in Tennessee. Hidden within the Craighead Caverns in Sweetwater, this enormous body of water lies in a cave system filled with fascinating formations, such as stalactites, stalagmites, and rare anthodites, also known as "cave flowers."

A National Natural Landmark, this lake marvels scientists, who are yet unaware of the exact extension of its waters. Those who visit can embark on a boat ride called "The Lost Sea Adventure," first walking inside the cavern before reaching a boat to navigate these ethereal sights.

7

Mammoth Cave National Park

Image: Sherin Jacob

The Mammoth Cave National Park is home to the longest cave system in the world . Located in central Kentucky, it extends over 420 miles of explored passages and many more likely undiscovered. Enormous chambers, underground rivers, a labyrinth of tunnels, and gypsum crystal formations can all be found at this site.

The park has been declared a UNESCO World Heritage Site and an International Biosphere Reserve. It also includes over 52,000 acres of protected land on the surface, renowned for its lush forests and diverse wildlife.

8

Carlsbad Caverns National Park

Image: Cason Asher

A large bat colony lives in the Carlsbad Caverns National Park in New Mexico, but that’s not its only charm. The park boasts over 100 caves, with its centerpiece being the immense Carlsbad Cavern.

The cavern includes the Big Room, one of the largest underground chambers in North America, spanning 8.2 acres. Visitors can descend via an emblematic natural entrance or by elevator, dropping 750 feet underground. Stalactite formations like the Giant Dome, the Hall of the White Giant, and the Chandelier are some of the caves' breathtaking highlights.

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Indian Echo Caverns

Image: Magda Ehlers

The Indian Echo Caverns, which have been open to the public since the early 1920s, are carved into the limestone of the Appalachian Mountains. Located near Hummelstown, Pennsylvania, this site gets its name from the echoes heard within the cavern’s chambers , which were once believed to be mystical by Native American people in the area.

Unique, immersive sections of the caverns have names like the "Crystal Palace," the "Echo Room," and the "Wedding Room," where, yes, real weddings are sometimes held!

10

Wind Cave National Park

Image: Francesco Ungaro

Wind Cave National Park, located in the Black Hills of South Dakota, is one of the world’s largest caves, but that’s not what it’s most famous for. One signature sight here is the boxwork formation , a rare lattice-like pattern formed by calcite deposits.

The cave system stretches for over 140 miles, though much of it remains unexplored. Popular tours take guests through captivating features like the "Ribbon Room" and the "Crystal Palace."

Why is Wind Cave called that? Mainly due to the "wind" phenomenon that occurs at its entrance. The cave's air pressure causes the entrance to draw in or expel air, depending on atmospheric conditions.

1

The first post office? A Boston tavern

Image: Mick Haupt

In 1639, the first organized mail service in British North America started at Richard Fairbank’s tavern . The owner collected and distributed mail brought by ship.

Although informal and modest by today’s standards, this post office laid the foundation for communal mail collection and delivery.

2

Enter Benjamin Franklin

Image: Brett Wharton

From 1753, Franklin served as joint Postmaster General for the colonies and undertook a sweeping reform: he organized delivery routes, aligned them with major roads and rivers, and cut the mail travel time between Philadelphia and New York to about 33 hours .

He also introduced the first rate chart, standardizing delivery costs based on weight and distance, turning what had been a scattered courier network into a more reliable, structured mail system.

3

National Postal System founded

Image: David Trinks

With the American Revolution underway, the Second Continental Congress established the first national postal agency in 1775 , appointing Benjamin Franklin as the first Postmaster General.

This new postal service initially handled mostly military and diplomatic correspondence, but the agency laid the groundwork for what would become a national communications service.

4

The Age of Steam: mail by steamboat

Image: mandylin

In 1813, Congress authorized the Postmaster General to contract steamboat companies to carry mail. Soon, steamboats were ferrying mail up and down the East Coast and the Mississippi River .

By 1848, mail even traveled to California via steamship and across the Isthmus of Panama, a three-week voyage.

5

Overland stagecoaches and the Butterfield Overland Mail

Image: Ricky BiggsSr

Between 1858 and 1861, the Butterfield Overland Mail stagecoach service carried U.S. mail across the western frontier, from eastern posts like Memphis and St. Louis to San Francisco .

This service helped connect the eastern U.S. with rapidly growing western settlements long before the completion of the transcontinental railroad.

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Railroads enter the picture

Image: Jay Kettle-Williams

As railroads expanded, the postal service started to use this new technology: in 1832, the first mail deliveries by train were made.

Rail transport vastly improved speed and reliability compared to horse and stagecoach travel , and became a key advance as mail traffic increased and the nation expanded westward.

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First U.S. postage stamps

Image: The New York Public Library

In 1847, the first official U.S. postage stamps were issued: a 5-cent stamp featuring none Ben Franklin and a 10-cent stamp featuring George Washington .

Prepaid stamps simplified payment and collection of postage, removing complications from pay-on-delivery systems and helping the postal system function more efficiently.

8

The Pony Express

Image: The New York Public Library

In 1860, the Pony Express started its overland mail route between Missouri and California, nearly 1800 miles of relay horseback riding . The mail took 10 days between endpoints.

Although short-lived (it ended in 1861), the Pony Express demonstrated the demand for rapid cross-country communication.

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City-wide home delivery

Image: Lesli Whitecotton

In 1863, free city mail delivery began , allowing residents in major cities to receive letters directly at their homes rather than picking them up at a post office.

This represented a major shift: mail became a part of everyday domestic life, not just something dropped off and picked up by hand.

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Pneumatic tube mail in NYC

Image: The New York Public Library

In 1897, a pneumatic-tube mail system began operation in New York City. Mail could travel underground at high speeds, from the General Post Office to other offices in Manhattan within minutes .

At its peak, the system carried thousands of letters daily: at one point, nearly 30% of New York City mail went through this immense underground network.

11

Parcel post service launches

Image: Olivier Rouge

On New Year’s Day 1913, the U.S. Post Office inaugurated the first official parcel post service , allowing packages, not just letters, to be sent through the mail.

The impact was immediate: within the first five days, millions of packets passed through post offices, fueling mail-order business and expanding commerce everywhere.

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First airmail route

Image: Qihao Wang

In 1918, the postal service launched the first regularly scheduled air mail route between Washington, D.C., and New York , marking the beginning of mail carried by airplane.

Airplane mail allowed far faster coast-to-coast and long-distance communication, a major leap from sailboats, stagecoaches, or railroads.

1

Paul Bunyan

The giant Northwoods lumberjack and his blue ox, Babe, began as camp lore but became truly national once adman W.B. Laughead used him in Red River Lumber Company pamphlets. Those promotions helped standardize the tall-tale feats , like the myth that he carved all of Minnesota’s lakes with his axe or his footprints.

2

Johnny Appleseed

A real nurseryman turned folk saint, Johnny Appleseed (a.k.a. John Chapman) planted nurseries (not random seeds) on the frontier, selling or leasing saplings to settlers. Because cider drove apple demand, his work fit the era’s foodways and law.

Over time, he was mythologized as a barefoot, pot-hatted wanderer who "greened" the Midwest .

3

Pecos Bill

The ultimate cowboy hero who lassoes tornadoes and rides mountain lions . Though set in the mythic West, he’s a 20th-century creation: Edward O’Reilly’s 1917 stories (and later children’s retellings) created his outlandish feats.

4

John Henry

The steel-driving man who raced a steam drill and "died with a hammer in his hand" embodies labor dignity in the machine age. Ballads likely trace to late-19th-century railroad/tunnel work in the South. The story’s core made him a working-class icon and civil rights touchstone.

5

Davy Crockett

A real frontiersman and congressman whose image ballooned into legend via 1830s almanacs and later popular culture (most famously Disney’s 1950s series).

Known for the image of the coonskin cap on his head and his bear-wrestling bravado, his death at the Alamo sealed his heroic reputation.

6

Mike Fink

The "king of the keelboaters" of Ohio–Mississippi river lore, famed for marksmanship and pranks. A semi-legendary man, he eventually made it into folktales and later print stories. They all fixed him as the wild spirit of the river trade before steamboats took over.

7

Molly Pitcher

A Revolutionary War camp-follower-turned-artillery heroine in legend. She is often linked to the 1778 Battle of Monmouth. In reality, historians note that "Molly Pitcher" functions as a composite legend of different women, herself a symbol for women’s wartime labor.

8

The Headless Horseman

Washington Irving’s 1820 tale set in Sleepy Hollow cemented America’s most famous ghostly rider. The figure merges European motifs with Hudson Valley lore, and it eventually became a perennial of American Halloween culture.

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Sasquatch

The shaggy forest giant of the Pacific Northwest has Indigenous antecedents, but the modern media phenomenon exploded after 1958 reports of enormous footprints in Northern California. Since then, " Bigfoot " has fueled tourism, legislation proposals, and endless debate.

10

The Jersey Devil

South Jersey’s Pine Barrens " state demon ," long tied to the Leeds family legend and 18th-century quarrels, became a 20th-century media sensation. Descriptions of it vary, often including a mixture of different animal parts, such as a goat-horse head, bat wings, and cloven hooves. Although not everyone agrees on what it would look like, it is definitely a regional identity badge of New Jersey.

11

Mothman

Reported around Point Pleasant, West Virginia, this is a red-eyed, winged figure who allegedly predicted disasters, something that became even more popular when the Silver Bridge tragically collapsed. The 2002 film The Mothman Prophecies embedded it in pop culture: Festivals, statues, and a museum now anchor its local mythology.