The 9 Most Incredible Caves in the World

1. The Blue Grotto in Capri, Italy

The Blue Grotto is the emblem of Capri. It is a sea cave found on the coast of the island and is a well-known spot to all who visit the area. This cave is unique for its brilliant blue glow which comes from two sources: the entrance to the cave (a small opening where only one rowboat can enter at a time) and a bigger hole beneath the entrance. When viewed from inside the cave, the entrance appears as a brilliant white light just above the waterline, while the underwater hole, which is the larger source of light, provides a blue glow.

2. Cave of the Crystals in Chihuahua, Mexico
Miners first discovered the Cave of Swords, located directly above the Cave of the Crystals, in 1910. The crystals there are much smaller than in the Cave of the Crystals (a mere 1-2 meters versus a whopping 12 metres!), and the temperature is cool, which may be why the crystals stopped growing.

The Cave of the Crystals, on the other hand, was discovered in 2000 and contains the largest natural selenite crystals ever found. The biggest crystal found here was 12 meters in length and 4 meters in diameter! As opposed to the Cave of Swords, the average temperature here is 50-58 degrees Celsius with 90-99% humidity. Because of this extremely hot temperature, this cave is relatively unexplored. Even scientists and researchers with the proper protective gear can only stay in the cave for 30-45 minutes at a time.

So how were these incredible crystals formed? Over time, gypsum-rich groundwater began seeping into the cavern that is now the Cave of the Crystals, filling the hollow space with gypsum. This alone might not do much, but thanks to the pool of magma beneath the cave, the groundwater remained at 50 degrees Celsius for 500,000 years, allowing selenite crystals to form and grow to gigantic sizes.

Fun Fact: The Cave of the Crystals was only ever accessible because of the pumping operations of the mining company that was working in the nearby Naica Mine. Mining stopped in 2017, and the cave has since been re-flooded in an attempt to return it to an undisturbed state in which its crystals can continue to grow.

3. Krubera Cave in Abkhazia, Georgia
Krubera cave was discovered in 1960 and is the deepest-known cave on Earth, with a depth of over 2196 meters. Krubera cave is also known as the Voronja Cave, which means “cave of the crows” in Russian. This name was used in 1980 by speleologists because of a number of crows nesting at the entrance of the cave. The original name, Krubera, was given by Russian speleologists in honor of Alexander Kruber, a noted Russian geographer.

Important update: Since the discovery of Veryovkina Cave in the same area of Abkhazia in 2001, Krubera Cave became a close second. Veryovkina Cave has a depth of 2212 meters and is now the deepest cave in the world.

4. Fingal’s Cave in Staffa, Scotland

This incredible sea cave is located on the uninhabited island of Staffa in Scotland. The island is of volcanic origin and is famous for its distinctive hexagonal basalt columns, of which Fingal’s Cave is the most striking example. The cave’s size, shape, and naturally-arched roof combine with the waves to create eerie sounds that enhance its cathedral-like atmosphere. The cave was named after the hero in James Macpherson’s book Fingal, which means “white stranger.”

5. Eisriesenwelt Ice Cave in Werfen, Austria

This natural limestone ice cave is the largest of its kind, extending 42 kilometers into the earth and welcoming 200,000 tourists every year. Although the cave is massive, only the first kilometer of it is covered in ice and open to tourists. The rest of the cave is just limestone. The oldest layer of ice in the cave dates back 1,000 years!

Eisriesenwelt was formed by the Salzach river, which slowly eroded passageways in the mountain. The ice formations in the cave were created by thawing snow that drained into the cave and froze. This section remains icy even in the summer because the cave entrance is open year-round, leaving it exposed to chilly winds that keep the temperature below freezing. New formations appear each spring, however, as water drips into the cave and freezes.

6. Puerto Princesa Subterranean River in Palawan, Philippines
The Puerto Princesa Subterranean River National Park is one of the New Seven Wonders of Nature and a UNESCO World Heritage Site. The river is home to many marine creatures. The entrance to this cave is a short hike from a nearby town.

In 2010, a group of environmentalists and geologists discovered that the underground river has a second floor, creating numerous small waterfalls inside the cave. There is also a 300-meter cave dome above the underground river where one can see unbelievable rock formations, large bats, a deep hole in the river, river channels, and another deep cave.

There are also several large chambers found inside the cave, including the 360-meter Italian Chamber, which is one of the most massive cave rooms in the world.

7. Mammoth Cave National Park in Kentucky, USA
Mammoth Cave National Park is the longest cave system in the world. It spans 52,830 hectares (or 528.3 square kilometers), making it twice as long as the second longest cave system—Mexico’s Sac Actun, an underwater cave.


The National Park offers several tours, helping visitors discover numerous notable features of the cave, such as the Grand Avenue, Frozen Niagara, and the famous Fat Man’s Misery. These attractions are available for viewing on tours that can last up to six hours. More adventurous tours are also offered, such as those that venture away from the developed parts of the cave and into muddy crawlspaces and dusty tunnels.

(Not So) Fun Fact: The wildly popular Echo River Tour was discontinued in the 1990s because human traffic was endangering the aquatic creatures that live there.

8. Škocjan Cave in Divača, Slovenia

Škocjan Cave is home to some of the most significant underground phenomena both in the Karst region and Slovenia, earning it a spot as a protected UNESCO World Heritage Site. International scientific circles consider it to be one of the most important natural treasures on the planet.

9. Carlsbad Caverns National Park in New Mexico, USA
Carlsbad Caverns National Park consists of an extensive network of caves nestled deep in the limestone rock of the Guadalupe Mountains. It is one of the most visited caves in the United States, reaching 41 million visitors in 2011. It is open all year round, except for Christmas Day, and visitors have the option to either hike all the way to the entrance of the cave or use the elevator.

This cavern includes “The Big Room”—a massive chamber made of natural limestone. At about 4,000 feet long, 625 feet wide, and 255 feet high (at the highest point), it is the third largest chamber room in North America and the seventh largest in the world.

Carlsbad Caverns offers numerous programs for tourists. One of the most popular ones is the Bat Flight Program, where tourists can witness the bats’ sunset flight out of the cave and their sunrise flight back in the following morning. Camping is also allowed provided campers have a ticket from the National Park center.

A recent discovery revealed the Chocolate room and the bottomless pit. The latter was first thought to have no bottom because stones thrown into the pit made no sound. Later they found out that it is only 140 feet deep and has a thick layer of soft dirt at the bottom, which is why it doesn’t make a sound when stones land.

On top of being my personal favorite, this cave is a major tourist attraction and is famous worldwide. The glowworms are the size of ordinary mosquitoes, and millions of them abound inside the cave. They are monitored closely by specialized staff from a scientific advisory group that uses automated equipment to monitor the cave remotely, including the temperature, the amount of carbon dioxide (needed to maintain the glowworms), and the number of visitors that can enter each day.

The guided tours cover three levels and commence with a boat ride on the underground river, where the ceiling is lit solely by these spectacular glow worms. It’s like watching the night sky full of twinkling stars!

Fun Fact: This is the only place on earth where these glowworms, or arachna luminosa, can be found!

How Are Caves Formed?
In addition to appreciating the beauty of these amazing caves, it is important that we understand how they came to be. There are various types of caves in the world, and they are formed in different ways. I will give a very simple outline here, but if you’d like to learn more, visit the National Caves Association’s page on how caves are formed.

See world’s largest cave, Hang Son Doong, in Vietnam

Cave formation begins when acid rain is absorbed by the ground. Acid rain consists of rainwater mixed with carbon dioxide. As this acid rain travels through the ground, it comes in contact with solid rocks. If this rock is made of limestone or dolomite, the water will react chemically until it slowly dissolves the rock and a hollow space is formed. As the space becomes bigger, water begins to flow through it, eventually creating a stream or underground river.

At this point, erosion and weathering begin and further cave formation. After a thousand years, the hollow space is already big enough for a human to enter. After a million years, chambers and columns form due to erosion and the meeting of stalactites (from the ceiling) and stalagmites (from the ground), and spectacular caves like the ones you’ve seen here are born!


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