Have you ever had a hankering to watch hockey below the Earth? You might if you head to Norway, home to the world’s largest underground auditorium. Located nearly 400 feet below the surface is the subterranean auditorium known as Gjøvik Olympic Cavern Hall. The cavern is home to the local hockey league Gjøvik Mammuts and also features an 80-foot swimming pool.

Although Austria may be home to the world’s largest natural ice cave — the 26-mile-long Eisriesenwelt — Iceland can claim the world’s largest human-made ice cave. The cave extends about 1,600 feet into Langjokull Glacier and took more than four years and $2.5 million to dig into solid glacial ice. A group of Icelandic entrepreneurs dreamt up the project so tourists could visit the inside of a glacier instead of just scratching the surface.

Only accessible by boat, the Marble Caves found on Lake General Carrera in Chile were formed by 6,000 years of waves pounding into the surface of the rock and smoothing it out. The colors — often shades of blue, green, and gray — change based on water level. When water is shallow in the spring, the caves look turquoise; deeper water in the summer appears cerulean.

If you can’t decide whether you want to hole up in a cave or a castle, you’re in luck: Predjama Castle in Postojna, Slovenia, offers the best of both worlds. The 13th-century castle was built directly into the entrance of a giant cave that sits about halfway up a 400-foot cliff. Looming 115 tall, the castle holds the Guinness World Record for largest cave castle.

The stunning natural geological formations inside China’s Reed Flute Cave are amplified by a riot of electric color, thanks to multicolored lights stuffed inside the nooks and crannies of the limestone cave.. Signs of exploration within the cave date back to 792 CE, but it was rediscovered by refugees during World War II.

Located off Route 66 in Stanton, Missouri, the Meramec Caverns have drawn tourists for decades. But one of those supposed visitors stands out from the rest: outlaw Jesse James. In 1941, explorers of the 4.6-mile cave system claimed to have found artifacts connected to James, leading to the cave’s nickname as the “Jesse James Hideout.”

The 300 steps up to Batu Cave help make the spot one of the most colorful places in the world. The concrete steps are painted in bands of rainbow hues, and it’s just as colorful inside. The interior temple — an homage to Lord Murugan, who triumphed over the demons in Tamil Hindu lore — is also covered in similarly exuberant shades.

Stepping into the Cave of Crystals near Naica, Mexico, feels like walking onto another planet — massive mineral columns, larger than telephone poles, shoot out in every direction. The horseshoe-shaped cave, found by a mining company in 2000, creates an ideal environment for gypsum, also known as selenite, crystals to form.

In 1954, a mathematician and scientist named Leland W. Sprinkle visited the Luray Caverns of northern Virginia and was inspired to build the Great Stalacpipe Organ after noticing that the stone formations emitted a musical tone when struck. Sprinkle spent three years studying, selecting, and altering the stalactites in order to construct the organ. The end result is the largest musical instrument in the world.

More than 15 million Mexican free-tailed bats live in Texas' Bracken Cave, located 20 miles outside of San Antonio, which makes it the largest known bat colony on the planet. In summer, the bats often emerge en masse to search for food around three hours before sundown, which provides a stunning visual. The bats migrate south in late fall, so the best time to witness a flight is between July and August.

Vietnam’s Hang Son Doong cave covers an area that is more than three miles long and up to 650 feet tall. The cave is so large that it has its own ecosystem and localized weather system. While it’s estimated to be 3 million years old, a local farmer was the first to discover it in 1990, and exploration didn’t start in earnest until 2008.

The hexagonal columns of basalt that make up the interior walls of Fingal’s Cave in Scotland seem to match the structure of Giant’s Causeway in Ireland. A Celtic legend tells the story of Irish giant Finn McCool building a bridge from Ireland to Scotland in order to fight his nemesis, Benandonner. The remaining geometric columns are purported to be the end points of the giant’s bridge.

Lost River Cave in Kentucky is home to the world’s shortest and deepest underground river. Meandering only 350 feet long, the river flows 427 feet below the earth’s surface, linking to a second underground river which hasn’t been fully explored. The cave has served as shelter for early Native Americans since the end of the last ice age, and 10,000-year-old spear points have been discovered within.

Eisriesenwelt in Austria is the world’s largest ice cave, with layers of ice dating back approximately 1,000 years. The cave is continuously carved by water entering and freezing every year, which means that it’s still growing. Only the first half-mile from the entrance is covered in ice, but cold air continues to flow through the rest of the corridors and chimneys.

The Waitomo Caves on the North Island of New Zealand resemble a sparkling forest full of fireflies, thanks to a unique insect that calls them home: the Arachnocampa Luminosa, aka the glowworm. Thousands cover the cave walls and ceilings, lighting it up with their bioluminescence, which can be seen on boat tours.

With 173 square miles of glaciers, Washington is the second-most glaciated state after Alaska. The Big Four Ice Caves are among the state’s most fascinating glaciers. The glacial caves are formed by winter and spring avalanches on Big Four Mountain. The snow typically melts from August to October, allowing adventure-seekers to visit the ice caves along the popular Big Four Ice Caves Trail.

Speleologists are those who study caves, and according to their specific scientific vocabulary, an active cave is one that has water flowing through it. A relict cave, however, does not. There are also different types of active caves, like inflow caves, outflow caves, and through caves, which are named depending on where the cave water starts and ends.

Spelunkers, take note: Tennessee has a lot of caves — nearly 10,000, in fact, making it the most cavernous state in the country. The lion's share of these natural formations can be found in the eastern portion of the state near the Appalachian mountains. Among those open to the public for exploration are Cumberland Caverns, the Bell Witch Cave, and the Lost Sea.

Kentucky’s Mammoth Cave is the world’s longest by distance. More than 400 miles of caves have been mapped so far, and according to park estimates, there are another 600 miles left to discover. The centerpiece of Mammoth Cave National Park, established in 1941, the massive underground labyrinth draws more than 2 million visitors every year.

At more than 7,200 feet deep (and eight miles long), Krubera Cave in the western Caucasus mountains of Georgia is the deepest in the world. At the base, the cave is filled with water, but in 2012 a Ukrainian diver reached about 170 feet further down into the cave. There are underground campsites spread throughout the massive system for those exploring the cave.