For centuries, cultures and religions around the world have used caves for worship, meditation, art, and burial. But what makes these places so special? Quite a lot, actually — there is a fascinating world hidden beneath our feet. Today, we’ve compiled a list of 10 of the most famous caves from around the globe, each unique in its formation, appearance, and features. You’ll see that these formations are not always dark and gloomy — some are glowing, blue, or even shaped by artificial forces. Let’s explore them.
Italy’s Blue Grotto Cave, the Most Blue Sea Cave
The Blue Grotto, on the coast of Capri, is famous for its intense, otherworldly blue water. Known to the Romans in antiquity, the cave was rediscovered in 1826 by German poet August Kopisch. Its striking color is caused by sunlight passing through an underwater opening and refracting off the white sandy seafloor, filtering out red light and leaving only a vivid blue glow. Without this light effect, the cave would appear dark and unremarkable. The entrance is so low that visitors must enter in small rowboats, lying flat to pass beneath the rock arch during calm seas. Unlike many other sea caverns, swimming inside is prohibited to preserve its delicate environment.
Kentucky’s Mammoth Cave, the Longest Cave System
The Mammoth-Flint Ridge Cave System is the longest karst cave system in the world and is likely to remain so for the foreseeable future. It spans 52,830 hectares. Exploration has mapped over 587 kilometers of the system, including 225 underground passages, approximately 20 large chambers, and 20 deep shafts. The National Park, named after the rock formation, offers a variety of guided tours for visitors. Notable highlights include the Grand Avenue, the Frozen Niagara, and the famous Fat Man’s Misery passage.
New Zealand’s Waitomo Glowworm Caves, the Glowiest Cave
The Waitomo limestone cave network attracts over one million visitors annually. The rock formation was known to the Māori for centuries, but Europeans discovered it only in the late 19th century. Tourism began here in 1911. It features notable formations such as the Organ, the Catacombs, and the Tomo — a deep limestone shaft. The Glowworm Grotto is illuminated by a natural phenomenon: bioluminescence. The light is produced by male Arachnocampa luminosa glowworms to attract females. Without this unusual glow, the area would be in complete darkness. By the way, in addition to the Glowworm Grotto in Waitomo, there is the dry Cathedral Cave with excellent acoustics — once, the famous opera singer Kiri Te Kanawa even performed there.
Vietnam’s Son Doong Cave, the Largest by Volume
In Vietnam’s Phong Nha-Kẻ Bàng National Park lies Sơn Đoòng Cave — the largest known cave by volume on Earth. Formed around 2–5 million years ago when river water eroded away limestone, it stretches over 5 kilometers (3 miles) and reaches heights of more than 200 meters (660 feet). The interior is so massive it contains its own river, a dense jungle, and even localized weather, with clouds forming inside. Its scale is so immense that a Boeing 747 could fly through its largest chamber without touching the walls.
Georgia’s Veryovkina Cave, the Deepest in the World
Veryovkina Cave is located in the Arabika Massif of the Gagra Range in Abkhazia, Georgia. This remote karst region, overlooking the Black Sea, is home to some of the world’s most challenging cavern systems. The area was first identified in 1968 by Soviet speleologists, but its true depth was only confirmed decades later through modern expeditions. Veryovkina is the world’s deepest known cave, reaching a record-breaking vertical depth of 2,212 meters from its highest entrance to its lowest explored point. Its immense depth makes it a unique and extreme geological feature — and one of the greatest prizes in the world of speleology.
The cavern was carved over millions of years by water seeping through soluble limestone, gradually creating a network of vertical shafts, narrow passages, and vast chambers. Seasonal underground rivers and waterfalls continue to shape its interior, adding to its complexity. The journey to the bottom involves traversing sheer drops, rope descents, and flooded tunnels, making it one of the most technically demanding explorations on Earth.
The cavern is not open to casual tourism due to its extreme conditions. Only elite cave exploration teams have descended to its deepest point, facing days underground in freezing temperatures, with constant risks from flooding and rockfall. For the speleological community, it stands as the ultimate test of skill, endurance, and preparation — and a symbol of how much of the underground world remains unexplored.
Hawaii’s Kazumura Cave, the Longest Lava Passage
Kazumura Cave on the Big Island of Hawaii is the longest known lava tube in the world, stretching for over 65 kilometers. Formed by flows from the Ailā‘au eruption about 500 years ago, it descends more than 1,100 meters, making it not only long but also one of the deepest lava tubes. The earliest records of it were in 1966 when it was used as a fallout shelter. Its system contains rare formations such as lava stalactites, lavacicles, and intricate “rope” patterns left by cooling molten rock. It is also home to unique cave-adapted species, including blind cave crickets found nowhere else on Earth. Exploration requires permits, and parts of the system are accessible only through vertical shafts.
Austria’s Eisriesenwelt, the Largest Ice Cave
The name of the world’s largest system of ice caves (located 40 km south of Salzburg) translates from German as “Giant Ice World.” This frozen realm stretches for an astonishing 42 km, though visitors are only allowed into the first kilometer — more than enough to leave a lasting impression.
Inside are fantastically shaped ice flows and frozen waterfalls, formed from meltwater snow that entered the cave about a thousand years ago and solidified into extraordinary forms. Today, cold winds blow through the cavern in winter, while in summer, frigid air from its depths prevents the ice from melting.
The first chamber on the tourist route, reached via an ice tunnel, is the Posselt Hall, featuring a massive central stalagmite. From here, visitors can glimpse the Great Ice Embankment — a 25-meter-high wave of solid ice. Other highlights include the castle of the mythological giant Ymir, the Ice Organ, and, at a depth of 400 meters below the surface, the Ice Palace. All formations are artfully illuminated, creating the eerie yet breathtaking impression of stepping into a frozen fairy tale.
México’s Sistema Sac Actun, the Longest Underwater Cave
In the labyrinth of underground caves beneath the jungles of Quintana Roo, on Mexico’s Yucatán Peninsula, flows the longest known underground river in the world. It also holds the title of one of Mexico’s most remarkable natural wonders, famed for its striking geological formations. The twists and turns of its watercourse run through limestone caverns for 386 km. This river is part of the Sac Actun system, whose name means “white cave” in the Mayan language.
China’s 816 Nuclear Plant, the Largest Artificial Cave
The 816 Nuclear Plant is an unfinished Cold War–era underground nuclear weapons facility in the Fuling District of Chongqing, China. Concealed within a mountain and surrounded by dense forest, it is considered the world’s largest man-made cave, covering over 104,000 square meters. Built between 1966 and 1984 by more than 60,000 workers, it was intended to produce weapons-grade plutonium but was never completed or used. Declassified in 2002 and opened to the public in 2010, the site now offers tours through its vast tunnels and chambers, revealing a remarkable relic of Cold War history.
México’s Cueva de los Cristales, the Biggest Crystal Caves
The Cave of the Crystals lies 300 meters below Naica Mountain in Chihuahua. Discovered in 2000, it contains some of the largest natural crystals ever found, with selenite formations reaching up to 11 meters long and weighing over 50 tons. The cave’s extreme conditions — temperatures near 58°C (136°F) and humidity close to 100% — make it inaccessible without special protective gear. Formed over hundreds of thousands of years in mineral-rich groundwater, it remains one of the most extraordinary subterranean environments on Earth.