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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.

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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.

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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.

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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.

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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 .

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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.

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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.

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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!

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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

Bannerman Castle, New York

Image: Erim Berk Benli

This crumbling fortress sits on a tiny island in the Hudson River, looking like something straight out of a Gothic novel . Francis Bannerman VI built it in 1901 to store his surplus military weapons because, apparently, his wife refused to keep thousands of munitions in the basement anymore.

The castle partially exploded in 1920 when some gunpowder got a little too excited, and it's been slowly deteriorating ever since. You can kayak out to the island or take a boat tour to see the ruins up close, where nature is slowly reclaiming the stone walls in a beautiful, apocalyptic sort of way.

2

Fonthill Castle, Pennsylvania

Image: Leyla M

Henry Mercer built this concrete monstrosity between 1908 and 1912. The guy was obsessed with tiles and built his castle as a showcase for his handmade ceramic collection , resulting in 44 rooms, 32 stairwells, and 18 fireplaces.

The castle has no blueprints because Mercer apparently just made it up as he went along, adding rooms and towers whenever the mood struck.

3

Gillette Castle, Connecticut

Image: Darya Tryfanava

William Gillette, famous for playing Sherlock Holmes on stage, built this eccentric castle in the 1910s and filled it with spy mirrors, secret doors, and wooden locks he carved himself . The place looks like someone dropped a medieval fortress into a blender with a detective novel.

The castle has 47 doors, none of which work like normal doors should, because Gillette apparently thought regular doorknobs were for boring people. Now it's a state park where you can wander through rooms designed by someone who clearly never met a quirk he didn't like.

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Boldt Castle, New York

Image: Pascal Bernardon

George Boldt started building this Rhineland-style castle in 1900 as a Valentine's Day gift for his wife Louise . Then she died suddenly in 1904, and he immediately halted construction and never returned, leaving behind a monument to heartbreak on Heart Island in the Thousand Islands.

The castle sat abandoned for 73 years until the Thousand Islands Bridge Authority took it over and began restoration. Today you can visit via ferry and explore the grand halls, the powerhouse, and the perfectly intact bowling alley.

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Castello di Amorosa, California

Image: Museum of New Zealand Te Papa Tongarewa

This one's a bit of a cheat since it was built in 2007, but it's so ridiculously authentic that it deserves a spot . Winemaker Dario Sattui spent 14 years and $40 million building a 13th-century Tuscan castle in Napa Valley, complete with a moat, drawbridge, and torture chamber, because apparently wine tastings needed more medieval flair.

The castle used 8,000 tons of hand-chiseled stone and over a million antique bricks imported from Europe. You can tour the dungeons, great hall, and of course, taste wine in a setting that makes you feel like you should be wearing chainmail instead of your Costco polo shirt.

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Belvedere Castle, New York

Image: Birmingham Museum Trust

Perched on Vista Rock in Central Park, this miniature castle was built in 1869 as a Victorian folly —basically an expensive decoration that serves no practical purpose. It's now home to the Henry Luce Nature Observatory and offers panoramic views of the park, which is considerably more useful than its original job of just looking pretty.

The castle got a major renovation in the 1980s after decades of neglect left it looking more "haunted" than "enchanting." Today it's one of Central Park's most popular spots.

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Bishop Castle, Colorado

Image: Art Institute of Chicago

Jim Bishop started building this castle by himself in 1969 and worked on it for over 55 years until his death in 2024 . The hand-built stone structure rises 160 feet into the Colorado sky and includes towers, walkways, and a dragon that breathes actual fire—all constructed by one incredibly dedicated (and possibly slightly unhinged) man.

There are no railings on many of the precarious walkways because Bishop didn't believe in them. Admission is still free, though you might want to update your will before climbing to the top of the tallest tower, where the views are spectacular, and the safety regulations remain charmingly absent.

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Searles Castle, Massachusetts

Image: John Phelan

Edward Searles built this castle in 1888 in Great Barrington, Massachusetts, creating a 40-room mansion that combined Romanesque and Gothic styles into something that can only be described as "aggressively architectural." The castle features stained glass windows, carved woodwork, and enough turrets to repel a small army.

After changing hands several times, the castle is now home to the John Dewey Academy. You can't tour the interior since it's a school, but you can admire the exterior and imagine what it's like to do algebra homework in a building that looks like it should contain dragons.

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Kip's Castle, New Jersey

Image: Birmingham Museum Trust

This English Tudor-style castle was built in 1902 by textile businessman Frederic Kip on a mountain in Montclair . The castle features towers, battlements, and spectacular views of Manhattan, proving that even early 1900s commuters wanted homes with dramatic flair and manageable drive times.

The castle has been through various owners and purposes, including a brief stint as a Prohibition-era speakeasy, because apparently nothing says "secret illegal bar" like a castle. Today it's used for private events, but the grounds are part of a county park where you can hike around and pretend you're visiting distant relatives who happen to be slightly eccentric nobility.

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Chateau Laroche (Loveland Castle), Ohio

Image: ConlonTT

Harry Andrews started building this medieval castle in 1929 using stones from the Little Miami River , spending over 50 years creating his dream fortress. Andrews was inspired by his time in Europe during World War I and decided Ohio needed more castles, which is hard to argue with.

He built most of it himself using ancient techniques, including a primitive pulley system and sheer determination. Today, the castle is maintained by the Knights of the Golden Trail, a Boy Scout-like organization Andrews founded. You can tour the castle for a few bucks and marvel at what one man with too much time and enough river rocks can accomplish.

1

Point Roberts, WA: The 49th parallel accident

Imagine if you had to cross two borders just to get to the market for a gallon of milk. That’s actually a reality for residents of Point Roberts, Washington. That’s because, following the Anglo-American Convention of 1818, the 49th parallel divided Canada and the U.S. In 1846, the line was extended westward and then officially recognized by the International Boundary Commission in 1925.

However, a tiny tip of the Tsawwassen Peninsula poked out just below that line. Since then, the locals have lived in a boundary quirk. To get to the rest of Washington State by land, they must drive through Canada, show their passports, and do it all over again on the way back.

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Statue of Liberty: Common misconception

If you want to start a friendly argument at a dinner party, ask whether the Statue of Liberty lives in New York or New Jersey. The funny thing is, both answers are technically right . While the statue physically sits in the waters of the Garden State, Liberty Island is legally an exclave of New York. This dates back to a 1664 land grant by the Duke of York in a document so vague and confusing that it took a 1834 Compact between the two states to settle the deal. New Jersey gets the water and the submerged lands, but New York keeps the monument.

However, the Federal Government actually manages the site through the National Park Service (NPS), providing security and maintenance.

3

The State of Franklin: Failed 14th state

In 1784, three counties in North Carolina felt neglected by their government and decided to strike out on their own . They even elected a governor, John Sevier, and printed their own money. They came just two votes short of being recognized by Congress as a formal state.

Eventually, things got heated, and North Carolina sent troops, leading to a small civil war between the locals. By 1789, the dream of Franklin was buried, and the territory became part of Tennessee.

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Kentucky Bend

If you look closely at a map, there’s a piece of Kentucky that looks like it doesn’t belong. That’s the Kentucky Bend, also called the New Madrid Bend, a tiny peninsula in Fulton County that is almost completely separated from the rest of the Bluegrass State . The strange situation was the consequence of the massive series of earthquakes that took place in that area between 1811 and 1812, which were so violent they famously caused the Mississippi River to flow backwards for several hours. When the dust settled, the river had carved a new path that looped around this small patch of land, surrounded by Missouri and Tennessee instead of Kentucky. The 9 residents living there today go through Tennessee just to get to their home state.

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The State of Deseret: The empire that almost was

Imagine a state so big it makes Texas look tiny. That almost happened back in 1894, when Mormon pioneers proposed the State of Deseret. The territory comprised what we now know as Utah, most of Nevada, parts of Arizona and Colorado, and a massive chunk of the California coast, including San Diego.

Had it been formalized, it would have been a powerhouse with its own seaport and total control over the West. However, Washington, D.C. wasn’t so keen on one group having that much territory and power, so they whittled it down, and we ended up having the states we know today.

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The lawless "No Man's Land"

Have you ever wondered what happens when two governments simply give up on a piece of land? Between 1806 and 1821, there was a strip of land in what is now western Louisiana that was, literally, No Man’s Land. Neither the U.S. nor Spain, which owned part of the territory, could agree on the border, so they declared it "Neutral Ground" to avoid armed conflicts . The plan backfired as, with no laws to contain it, it quickly became a favorite for the outlaws in the West —meaning deserters and bandits hiding there were legally untouchable. The conflict was resolved by the 1819 Adams-Onis Treaty, which officially set the Sabine River as the legal boundary.

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The Republic of the Indian Stream

In the early 1830s, people living in a small area between New Hampshire and Quebec were fed up, and in this case, taxes were the problem. Both Canada and the US were trying to collect taxes, and nobody likes being double-billed . In 1832, the residents essentially said "neither of them can tax us" and formed their own country called the Republic of the Indian Stream. They had their own constitution and Capitol for four years, until 1836, when the militia marched on the disputed territory to reclaim the land. It wasn’t until 1842, when the land dispute and the double taxation were definitively resolved by the Webster–Ashburton Treaty, which assigned the land to New Hampshire.

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The Northwest Angle: Mapping mistake of 1783

When the Treaty of Paris was signed in 1783 to end the Revolutionary War, the mapmakers used a chart that was flat-out wrong. They thought the Mississippi River started much further north than it actually did. Because of that mistake, a piece of Minnesota got cut off from the rest of the country . To this day, the "Northwest Angle" is the only place in the lower 48 states north of the 49th parallel. Much like Point Roberts, you have to cross a massive lake or drive through Canada just to visit it.

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The District of Columbia’s "lost" corner

If you look at a map of D.C., you’ll notice it’s missing a chunk; it’s not a perfect square as it was originally intended. Originally, the capital was a perfect ten-mile square diamond , taking land from both Maryland and Virginia. But by 1846, things got tense. Residents in the Virginia portion, which included Alexandria and Arlington, were worried the federal government would abolish slavery in the District, which was the backbone of their economy. They successfully petitioned to have Virginia "take back" that portion of the land and subsequently changed the shape of the national capital forever.

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UN Headquarters: International territory

If you want to feel international, go to the United Nations Headquarters on the East River in midtown Manhattan, New York. Once you cross that gate onto the 18-acre site, you are technically leaving the United States. You don’t need to show your passport, but that’s international territory, which means it has its own laws , its own security force, and even its own postal service. It is a legal hole in the middle of New York City.