If you were asked to picture the most beautiful place in the world, you might imagine the cobbled streets of Paris or a Caribbean island. Alluring as they are, however, these sites might just be overhyped. Many of the planet’s greatest panoramas lie below the surface.

These caverns run deep below the earth and have morphed into some truly stunning rock formations over the millennia. Of course, many of them are as deadly as they are pretty, so visitors beware!

1. Salina Turda, Romania: Though it functioned as a salt mine for a thousand years, today the space is a tourist attraction that some call a “space-goth fantasy.” Extensive renovations in 2008 made it into one of the most bizarrely beautiful sights on Earth.

Guests can explore tunnels and balconies carved out of salt, or simply admire the cave walls lined with cylindrical lights. In stark contrast to its futuristic vibe, Salina Turda still houses some of the original mining equipment.

Flickr / Robert Anders

2. Cave of El Castillo, Spain: The ridges of Monte Castillo are stunning on their own, but the winding cave system within the mountain might be even more impressive. Archaeologists first explored the tunnels in 1903 and made a startling discovery.

The site contains the oldest-known cave paintings, a few of which date back to 40,000 years ago! The markings even include outlines of the painters’ hands, stenciled in the cave’s natural red pigments.

Cultura de Cantabria

3. Zhaishan Tunnel, China: Nowadays, classical music echoes throughout the stream and walkways of Zhaishan Tunnel. However, its creators had much less elegant intentions for it during the 1960s.

Flickr / uniquenikki

The Chinese military originally built the underground passageway and barracks to house and move troops in secret. Exorbitant costs compelled the army to abandon the tunnel before the National Parks system took it over in 1997.

Wikimedia Commons

4. Blanchard Springs Caverns, Arkansas: Tucked inside Ozark National Forest, this three-story system has wowed explorers since the 1930s. It’s considered a “living cave” since dripping water is still reforming the many rock structures.

Arkansas.com

5. Sistema Sac Actun, Mexico: This Yucatan peninsula location holds the distinction of being one of the longest underwater caverns in the world. Deep inside, divers have found the remains of a mastodon, as well as the oldest known human remains in the area.

Feel The Planet

6. Friouato Caves, Morocco: Spelunkers have gone nearly 300 yards down into this cavern but have yet to reach its deepest point — some think it might reach over 3 miles. Scientists suspect that early North Africans used to inhabit the caves as well.

Wikimedia Commons

7. Víðgelmir, Iceland: A volcanic explosion from over a millennium ago forged this circular tunnel through the Icelandic mountains. Fortunately, the passage has cooled off in the following years.

Flickr / David C. Jones

Aside from lichen, almost no life can survive inside the cavern. However, it has created mesmerizing ice formations and crystals. Tour guides shine colored lights through them to create a kaleidoscopic effect.

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8. Ohio Caverns, Ohio: Just about everybody in the greater Dayton area knows about this tourist friendly cave, but it lives up to the hype. It’s home to the Crystal King, a free-hanging stalactite that spans nearly five feet.

Flickr / Brian Timmermeister

9. Actun Tunichil Muknal, Belize: Visitors to this site can wade through a subterranean river while tropical fish zip by their legs. Notwithstanding the cave’s natural beauty, it also houses dark archaeological secrets.

Benedict Kim

The cave’s twists and turns hold shards of ancient Mayan pottery, as well as human skeletons. Based on their condition, these remains very well may have been sacrificial victims.

Belize Grand Jaguar Tours

10. Florida Caverns State Park, Florida: History buffs will thank the New Deal’s Civilian Conservation Corps for the expansion of this Sunshine State Cave. Guests come from all over to witness its bouquets of limestone stalactites and stalagmites.

Florida State University

11. Cave Stream Scenic Reserve, New Zealand: This underwater river cuts through a Kiwi mountain pass and covers almost six football fields. However, explorers have to be careful not to enter during periods of heavy rain.

jontynz

Still, any New Zealander will tell you the stream is worth the trip. Hikers can also enjoy massive rock formations and beautiful vistas, not to mention mass eel migrations during certain seasons.

Trover / Stoked by Saturday

12. Ape Cave, Washington: Long before its famous 1980 eruption, Mount St. Helens carved out this lava tube. Its one of the longest passages of its kind, stretching out over approximately 2.5 miles.

Ben Wagner

13. Kartchner Caverns, Arizona: This cave remained undiscovered until 1974, so it is untouched by vandalism or other human interference. However, the thousands of bats that roost there have known about it for some time now.

Arizona State Parks

14. Skocjan Caves, Slovenia: This UNESCO World Heritage Site includes one of the largest underground canyons on Earth. Over 100,000 make the trek out to Škocjan each year, though the caves frequently have to close due to flooding.

Nomad Photographer

15. Kraków, Poland: Sure, maybe visiting a mine isn’t your typical idea of fun. But when you go over 300 yards down into the Wieliczka Salt Mine, you’ll realize it’s well worth the trip. The workers down there had an interesting way of passing the time underground…

Xseon

They carved incredibly intricate designs and figures out of the rock salt! Given that Kraków began mining there in the 1200s, the workers had a ton of time to hone their craft and create a truly otherworldly sight.

Alexander Lukatskiy

Wieliczka actually produced table salt up until 2007. Now, it remains purely as a historical site, commemorating the incredible effort and artwork of the miners. Some top contemporary sculptors have also visited to contribute their talents. Of course, Kraków isn’t the only city hiding a massive secret — underground or otherwise.

16. Teotihuacan, Mexico: Just northeast of Mexico City lies a complex of colossal temples and pyramids. These are the ruins of Teotihuacan, once the greatest city in the Americas before its mysterious collapse in the sixth or seventh century.

Reddit / redditsusernamelimit

Archaeologists still have much to learn about this lost culture, but they have discovered a fascinating truth about the city’s layout: three key structures — the Pyramid of the Sun, Temple of the Moon, and Temple of Quetzalcoatl — follow a peculiar pattern.

Specifically, they line up with the stars in Orion’s belt! We have yet to figure how the Teotihuacans achieved this feat with rudimentary technology. However, historians guess that their purpose was to create a “City of the Gods” by making their home reflect the design of the heavens.

Star Registration

17. Paris, France: Without a doubt, the Eiffel Tower is one of the world’s most famous sights. Once visitors reach its top, however, they spend too much time enjoying the view to notice a secret hidden just a few feet away — just as the architect intended. 

Brady Dyer

Ignoring the critics who hated his design, Gustave Eiffel knew the tower would be a national treasure. He felt so confident, in fact, that he wanted his own space to take in the vista and entertain like-minded intellectuals. So he built a small apartment!

Wikimedia Commons / Aimé Morot

The apartment is out of use today, but guests can still peek in through the window. It contains much of its original furnishings, complete with mannequins of Eiffel and his good friend Thomas Edison.

Flickr / Serge Melki

18. Pohnpei, Micronesia: Over 30,000 people of all sorts of nationalities live on the isle of Pohnpei. However, none of them can claim to be part of the Saudeleur Dynasty that once ruled there. Their culture fell hundreds of years ago, though relics of their past still stand strong.

Flickr / April Moulton

The best record of Saudeleur glory is the ruined city of Nan Madol. With its stone walls sunken into canals, Nan Madol once gained a reputation as the Venice of the Pacific. These days, more people compare it to Atlantis.

Legend has it that a pair of wizards and a flying dragon created the city, and it’s a fitting story. For centuries the ruins have captivated visitors, including supernatural author H.P. Lovecraft, who set some of his works in Nan Madol.

ShareAmerica

19. New York City, New York: Most tourists don’t realize it, but the Big Apple’s real treasures are nowhere near the commercial bustle of Times Square. Roosevelt Island — a strip of land just to the east of Manhattan — holds one of the city’s eeriest buildings.

Atlas Obscura

During the late 1800s, Renwick Hospital treated New Yorkers who fell victim to the smallpox outbreak. Its doctors abandoned it for a more modern facility years later. Though it crumbled and decayed, some interesting tenants moved right in. 

Amazing Places Finder

Enough felines moved into the hospital grounds that Renwick is now a wild cat sanctuary! They roam within the ramshackle hospital walls, while humans are seldom allowed to enter — bad news for anyone looking for an affordable New York City apartment.

DNAinfo

20. Naours, France: Located just off the Somme river, the charming hamlet gives off every appearance of a quiet country town. But thanks to its role in World War I, Naours has some astonishing secrets lying just below its surface. 

To protect themselves and civilians from enemy attacks, Allied forces dug out an entire underground city! Winding rock tunnels connect over 300 rooms, where the town waited out bombing raids and firefights.

Visit Somme

If you visit Naours today, you can still see where Allied soldiers etched their names and other graffiti into the stone walls. They had little else to do while huddled together, but their efforts produced an astonishing historical monument.

Yahoo News / Francois Nascimbeni

21. Urfa, Turkey: In 1963, archaeologists came across a buried structure in the Anatolia region. Its towering pillars were impressive, but what really shocked the scientists was the site’s age. It appeared that this building dated back to the tenth millennium B.C.

By 1996, a German archaeologist named Klaus Schmidt began excavating the site, known as the Göbekli Tepe, in earnest. As he studied the layout and artifacts within, he came to believe that it was not a settlement, but a temple.

Hurriyet Daily News

His research suggested this may even be the oldest place of worship on Earth! With Schmidt’s passing in 2014, however, we may never know exactly who constructed the Göbekli Tepe or how they moved these massive stones.  

22. Chattanooga, Tennessee: If you look closely at some of the buildings in downtown Chattanooga, you’ll notice some odd inconsistencies. For instance, is that the top of a window just inches above the sidewalk?

Atlas Obscura / Daniel Jackson

Surprisingly enough, there’s an entire underground city beneath Chattanooga! It follows the same grid of buildings and streets, and nobody is quite sure why it’s there. The documentation was likely lost years ago. Still, historians have a compelling theory.

WTCI

Tennessee suffered a devastating flood in 1867. Chattanoogans, hoping to prevent further disasters, may have raised the street level by 15 feet. As a result, they abandoned entire rooms and buildings. Brave explorers can still go down and see the filled-in windows and tattered wallpaper.