20 Fascinating Natural Caves

1. Cueva de los Cristales Mexico- Discovered in 2000 by two brothers who were drilling below the Naica mine near Chihuahua, the Cave of Crystals is a glittering spectacle with temperatures that can reach up to 112 degrees. Many of the crystals, which are estimated to be about 600,000 years old, can be several feet thick, and the smaller ones are razor sharp.

2. Grotto Azzurra Italy- If you're ever near Capri, Italy, you NEED to take a trip to the Blue Grotto. Once thought to be inhabited by sirens and devils, the cave is known for its radiant blue water. When the sunlight enters the cave through an underwater entrance, the water filters out the red light and leaves only the blue light to illuminate the cavern.

3. Phraya Nakhon Cave Thailand- Inside the Khao Sam Roi Yot National Park is the Phraya Nakhon: an incredible cave with an interesting history behind it. Sunlight filters through the top of the structure's collapsed ceiling, illuminating the Kuha Karuhas pavilion that was originally built in 1890 for King Chulalongkorn. Since it's construction, other local kings have visited the cave and left their signatures on it's walls.

4. Vatnajokull Glacier Cave Iceland- Formed entirely out of ice, glacier caves are best to visit in the autumn and winter, when the ice isn't as likely to collapse and the glaciers don't move as quickly. Many of them also take on a bright blue color, which is common in parts of glaciers such as the underside, or in this case, the inside which have not been turned white by the sun's UV rays.

5. Dongzhong Cave China- It's thousands of years old, but now, this otherwise ordinary cave serves as a classroom for 186 students and eight teachers. Meaning "in cave" in Chinese, Dongzhong began its role as an educational structure in 1984 and is now one of the coolest schools around.

6. Cave at the Mutnovsky volcano Russia- It may seem crazy to think that an ice cave could form at the base of a volcano, but that's the sort of thing that tends to happen in Russia. Hot springs have carved out the caves incredible shapes, while light that filters in through the roof creates an incredible color display of greens, purples, and blues. Many of those who have found the cave stumbled upon it by accident while exploring the area around the volcano, making this mysterious ice structure even more incredible.

7. Fingal's Cave Scotland- Although this cave on Staffa Island looks like it was painstakingly hand-carved by someone with an affinity for hexagons, its incredible geometric structure is completely natural. Hot lava that helped form the cave cooled and cracked in a hexagonal pattern. As the cracks extended down the mass of lava and shrank, it created the columns that the cave is famous for today.

8. Ellison's Cave USA- Northeast Georgia is home to Ellison's cave, which contains the appropriately-named Fantastic cave pit. At 586 feet deep, it's the deepest known cave pit in the United States and a dream come true for a dedicated rappeler. A rock dropped from the top is said to take about eight seconds to reach the ground.

9. Reed Flute Cave China- The Reed Flute cave has been a popular destination for well over a thousand years, as evidenced by transcriptions inside that date back to 792 AD. It was named for the reeds that grow just outside the entrance, which can be made into flutes. The formations inside the cave are just incredible, and combined with all the surreal lighting, they prove that amazing things can happen when man and nature's efforts combine.

10. Waitomo Glowworm Cave New Zealand- Formed over 30 million years ago, this cave is one of the most brilliant displays of bioluminescence on Earth. Thousands of glowworms, which are native to New Zealand, hang from the walls of the cave from strands of silk and use their dazzling blue light to attract prey.

11. Aven Armand France- If you dare to venture 100 meters underground, the Aven Armand will make it worth your while. It boasts over 400 unique types of stalagmites, including the largest one known in the world, which stands at nearly 100 feet tall.

12. Eisriesenwelt Ice Caves Austria- The world's largest ice caves were discovered in the late 19th century, which is pretty late considering how awe-inspiring they are. The entire labyrinth stretches twenty-five miles, and just like all ice caves, it's structure both outside and inside is constantly changing due to the ice that melts and refreezes. Any dedicated spelunker would be missing out if they didn't check out Eisriesenwelt.

13. Son Doong Cave Vietnam- The world's largest cave is located in Vietnams Quang Binh province. First found by a local man in 1991, the cave is nearly 700 feet wide, 500 feet high, and almost six miles long. Many of the cave's structures that have formed in its millions of years of existence are massive enough to make explorers appear minuscule in comparison.

14. Marble Caves Chile- Crystal-clear water tinted a dazzling blue by glacial silt accentuates the intricate designs in what many call he most amazing cave network in the world. The water is also responsible for forming the unique shape of the caverns and walls, making an Earthly cave appear very otherworldly.

15. Carlsbad Caverns USA- Located in what is now New Mexico, the Carlsbad Caverns National Park is home to many impressive caves, all of which were created between 4-6 million years ago. Sulfuric acid formed from mixed water dissolved the area's limestone, widening cracks in the rock and eventually creating the caves we know today. What makes these caves truly notable, though, are the massive deposits of gypsum, clay, and silt, whose presence gives the caves a fantastical and almost cartoonish look.

16. Barton Creek Cave Belize- When you first enter this cave, you might not find it to be anything too special until you notice the skulls. Barton Creek Cave was used by the Maya for ceremonial and burial purposes, and many of their artifacts and remains still lie amongst the cave's natural geological formations.

17. Kyaut Sae Cave Myanmar- According to legend, Kyaut Sae Cave was originally used as a place of hiding for locals who wanted to hide from the Mongols in the 13th century. Now, the cave has another special purpose. A Buddhist temple, which was built on the side of a cliff, is the entrance to the cave, which acts as a meditation area for monks.

18. Jeita Grotto Lebanon- Upon entering the Jeita grotto, you immediately understand why its name translates to "roar" of water. The lower grotto floods your ears with the sounds of the rushing water and air, which echo through the cave's chambers. As you travel deeper, though, the sounds of nature are replaced by a deep silence, allowing you to look around and take in the dazzling beauty of the cave's intricate geography without any distractions.

19. Cango Caves South Africa- In the Western Cape Providence of South Africa lie a series of caverns with dramatic and colorful limestone features. Artifacts show that many of the main cave entrances once served as homes for people living in the Middle and Later Stone Ages, but now the structures are used for tours for those who love a bit of adventure. Although about four kilometers of the caves have been discovered, only a quarter of that is open to the public.

20. Ordinskaya Russia- Exploring Ordinskaya, or the Orda Cave, in Russia's Ural region is the perfect adventure for anyone who enjoys their time in the water. The cave consists of over 3 miles of underwater chambers, and while it is possible to get lost, rest assured that seeing where you're going won't be an issue the water is so clear that you can see up to fifty yards ahead.