Caves are perhaps one of the most unexplored and inhospitable environments found on Earth. Despite this apparent inaccessibility, however, explorers and adventurers continue to seek and find entirely new subterranean worlds around the world. Some of the most fascinating caves we know of are also unique, thriving ecosystems, housing a number of species with adaptations not found anywhere else on Earth.
10. Marble Caves, Patagonia
Estimated to be over 6,000 years old, the Marble Caves are located on the Chilean side of General Carrera Lake in the Patagonia region of South America. Over the years, the lake’s turquoise waters, enriched with calcium carbonate from the nearby glaciers, have gradually dissolved and eroded the underlying limestone rock, giving way to the intricately-sculpted, marble-like formations that we see today.
Apart from their distinct, marble look, the striking blue hue of the lake – caused by suspended particles and reflecting sunlight – gives the whole place an otherworldly look, adding to its appeal for adventurers from around the world. Accessibility to the caves is still weather-dependent, however, owing to the harsh terrain of the area and the rough waters of General Carrera Lake.
9. Cave Of The Crystals, Mexico
The Cueva de los Cristales – also known as the Cave of the Crystals – was discovered in the year 2000 beneath the Sierra de Naica mountain in Chihuahua, Mexico. It was an accidental discovery, made during a regular dig by a mining company. The crystals are now known for their extraordinary dimensions – as some of them were found to be close to 40 feet in length – as well as their unique, almost-alien appearance.
As the scientists later found out, the crystals are composed of gypsum – a hydrated calcium sulfate mineral formed by tens of thousands of years of volcanic activity beneath the Naica mountains. This natural process is called hydrothermal mineralization, resulting in the colossal gypsum crystals found in the cave today. Sadly, the extreme weather conditions inside the cave make it difficult for casual travelers and explorers to regularly visit them.
8. Ajanta Caves, India
Ajanta Caves in India are a UNESCO World Heritage site known for their unique rock-cut Buddhist cave temples. Located in the Aurangabad district of the state of Maharashtra, these ancient caves are believed to have been built between the 1st century BC and 7th century AD, and are known for the fresco-type art found all over their walls and ceiling.
Ajanta Caves were carved out of a volcanic section of rock in a horseshoe-shaped gorge, and primarily consist of 30 rock-cut sanctuaries and monasteries that dot the picturesque, mountainous landscape. Historically speaking, their construction could be divided into two separate phases – from the Satavahana period between the 2nd century BCE and 1st century AD, to the second phase under the Vakataka dynasty between the 5th and 6th centuries AD.
7. Waitomo Glowworm Caves, New Zealand
The glowworm caves in the Waitomo region of New Zealand have been under formation for more than 30 million years. Named for the various species of bioluminescent worms that inhabit it, especially the native Arachnocampa luminosa, it’s a unique natural structure that continues to attract tourists and adventurers from all over the world.
The Glowworm Caves of Waitomo were first mapped by a local Maori chief, Tane Tinorau, along with a British surveyor called Fred Mace. Visitors can explore the cave system through guided boat tours along the underground river passing through the structure, with the sight of thousands of glowworms illuminating the cave ceiling like a starry night sky.
6. Eisriesenwelt, Austria
Also known as the world’s largest ice cave, Eisriesenwelt – translated to ‘World of the Ice Giants’ – is one of the most-visited natural tourist attractions in the Salzburg region of Austria. At more than 26 miles in length, it’s longer than most regular caves we know of, and its formation could be traced back to at least 100 million years ago.
The cave system owes its existence to multiple natural processes, including water erosion and the natural movement of tectonic plates. While it’s popular among adventure and cave enthusiasts from around the world, only the front portion of the cave is open for public visits, as the rest is made up of over 25 miles of chilly, mostly-inaccessible caverns and rooms. The entire structure remains cold throughout the year due to cold winds from outside, keeping the accessible part intact and frozen at all times.
5. Kamchatka Ice Cave, Russia
The Kamchatka Ice Cave is one of the many unique natural features found in the remote Kamchatka Peninsula in far-eastern Russia. Formed by the freezing and thawing actions of the vast glaciers of the region, the cave is nearly 0.6 miles in length, and stretches deep underneath the glacier like a natural archway made up of ice.
The cave’s formation could be attributed to the dynamic interplay between glacial movements and freezing temperatures of the region, resulting in the creation of the unique subglacial chamber we see today. Because of the volcanoes, the roof of the cave has melted to illuminate the chambers in the past few decades, giving the whole place an eerie vibe.
Apart from the cave, the Kamchatka peninsula boasts of many other extraordinary natural features, like volcanoes, geysers, grassland, and snow-capped mountains. To experience the region at its finest, the best time to visit is summer, when the weather is milder and the caves are accessible for exploration.
4. Blue Grotto, Italy
The Blue Grotto, translated to Grotta Azzurra in Italian, is a sea cave located on the island of Capri in southern Italy. The cave, formed through the relentless erosive action of the Tyrrhenian Sea, is a popular – even if rare – natural attraction on an island known for its upscale hotels and fancy markets.
Situated on the northern coast of Capri, the Blue Grotto is accessible via small boats ferrying visitors through its narrow entrance. The cave itself is quite large, however, with dimensions of about 200 feet in length, 80 feet in width, and 490 feet in depth. According to archeological studies done in the past few decades, the cave system is full of sculptures from Roman times, as we know that it was used as a private swimming pool during the reign of Emperor Tiberius.
3. Sistema Sac Aktun, Mexico
At a total length of more than 200 miles and maximum depth of more than 390 feet, the Sistema Sac Aktun is easily the longest underwater cave on Earth. Located along the Caribbean coast of the Yucatan Peninsula in Mexico, it’s a part of one of the most extensive underwater cave systems we know of. Until now, more than 220 cenotes – or sinkholes – have been discovered along its length, most of them formed by the collapsing ceiling of the cave.
Exploration of the region began in 1987, when various teams of divers and other experts began to map the network of caves found in the state of Quintana Roo. Also known as the ‘white cave’, the Sistema Sac Aktun is now known for its size and the diverse array of flora and fauna found inside its multiple ecosystems.
2. Mammoth Cave System, USA
The Mammoth Cave System could be found in the Mammoth Cave National Park in Kentucky. At a length of about 350 miles, it’s the longest known cave system in the world, with many of its caverns and sections still hidden and unexplored.
Formed over millions of years through the dissolution of limestone by underground rivers, the cave system is home to an intricate network of chambers, tunnels, and passageways, with visually-stunning stalactite and stalagmite formations at odd places. Unlike some of the other caves on this list, people have known about Mammoth Caves for a long time, as there’s evidence of Native American use and exploration.
Due to their historical and natural significance – as the caves are also home to a number of endangered species of plants and animals – the Mammoth Cave System has been classified as a UNESCO world heritage site.
1. Son Doong, Vietnam
The Son Doong is a large, famous cave located in the Quang Binh province of central Vietnam. At a height of about 650 feet and width of about 500 feet in places, it’s the largest known cave in the world by volume. As explorers have found out since its discovery back in 2009, the Son Doong is only a small part of an extensive, much-larger cave system in the region, about 70% of which remains completely unexplored.
The cave was accidentally discovered in 1990 by a local called Ho Khanh, though it was only fully explored by a team of scientific experts by 2009. According to studies, the Son Doong has been millions of years in the making, as the slow, gradual erosion of limestone gave way to the vast cavern that we see today. The inaccessibility of the structure, however, makes any long term scientific exploration impossible – any exit and entrance into the Son Doong requires a vertical ascent or descent of at least 280 feet.