If nature’s best-kept secrets are to be listed, natural caves make up for an unparalleled adventure. Caves are generally formed in four ways: rainwater, wind erosion, volcanoes, and sand erosion. Having geological formations, stalactites, stalagmites, and lakes, they are spectacular in many ways.

Caves have fascinated people of the 21st century but during prehistoric times, they have been used for shelter, safety, and ceremony. Here are ten incredible caves all over the world that tourists will be eager to visit—where tours are permitted.

10 Son Doong Cave, Vietnam

Popular for being one of the largest caves in the world, Son Doong Cave in Vietnam is one of a kind. Translating to “River Mountain Cave,” it is believed that the cave has been formed by river, Rao Thuong River erosion into the base of a limestone mountain, Truong Son. Hence, a large tunnel was formed underneath the tunnel.

Being 200m high and 175m wide as well as 9.4km in length, this cave is estimated to fit a 40-story New York skyscraper.

The most fascinating elements are a thick forest mushrooming in the cave for years as well as towering stalagmites, phytokarst, cave pearls, as well as cave roof, collapses. Also, It requires two days of intense jungle trekking and river crossings to reach the entrance of Son Doong Cave.

  • Cost: The expedition to this cave costs around $3000 for 4 days via Phong Nha-Ke Bang National Park Management Board (tour activities are operated by Oxalis Adventure)

9 Vatnajokull Glacier Cave, Iceland

One of the most spectacular caves in the world owing to its ice formations, Vatnajokull Glacier Cave in Iceland is worth exploring.

Though it earned acknowledgment after the shooting of the fantasy series, Games of Thrones, this glacier has been a quite crucial part of Icelandic culture. Located in the southeast of Iceland, Vatnajokull Glacier has more than 25 outlet glaciers and seven subglacial volcanoes.

Being the most voluminous glacier in entire Iceland, it covers around 8% of Iceland’s total area. However, the cave warns of danger during summer because of its melting ice and falling icicles.

Nevertheless, it's a heavenly beauty during winter.

To reach the glacier, one can rent a car from Reykjavik to Vatnajokull, which is around 237 kilometers.

8 Naica Mine Cave, Mexico

Indeed, a crystal mine, Naica Mine Cave in Mexico is located in Chihuahua, Mexico. The huge crystal cave in the mine is at a depth of nearly 400 feet and the cave walls are studded with crystals.

Boasting some of the largest naturally occurring crystals, especially selenite, this cave has a very hot and humid temperature. Hence, it can be visited only with proper caving equipment.

This cave is closed to the public at present and is explored solely by scientists for research purposes.

Related: Cave Diving: Five Cardinal Rules That Divers Must Abide By

7 Krubera Cave In Abkhazia, Georgia

The second-deepest cave in the world, Krubera Cave in Abkhazia has fascinated people all across the globe. With a whopping depth of 2196 meters, this cave can almost stack six Eiffel towers underneath.

The cave is shrouded in darkness and also has an underground frozen waterfall with some tunnels. Also, several endemic faunas have been discovered in this cave. The Russian geologist, Alexander Kruber discovered the cave up to 295 feet initially, it is named after him.

Despite being the deepest cave in the world, it is rarely explored due to the difficulty in the permission granted by Russia.

Only tourists with a Georgian visa before arrival in Russia are granted access to visit this cave.

To reach the cave, one can fly into Tbilisi, the capital of Georgia. A taxi or public transport from the airport to Kutaisi station for purchase of tickets towards Deep Capture Station.

The trip takes almost 16 hours which may sound overwhelming albeit it is dotted with remarkable destinations.

6 Glowworms Cave New Zealand

A cave that sparkles with thousands of glowworms, Glowworms Cave in New Zealand is an incredible adventure.

Located at Waitomo on the North Island of New Zealand, this cave has Arachnocampa Luminosa, the exclusive species of glowworms found in New Zealand. While this region was under the ocean for 30 million years, the limestone formation started occurring gradually.

The limestone of the cave is composed of fossilized corals, seashells, and fish skeletons which have been layered and compressed over years.

The tour of this cave is divided into three levels where visitors will visit 150 feet underground to witness the worms.

To reach this cave, it takes two hours from south of Auckland and the exit of State Highway 3 onto Waitomo Caves Road.

Related: Down We Go: Into The World's Longest Cave System

5 Batu Cave, Malaysia

Formed by the erosion of the Batu river, Batu Caves is a series of limestone caves located in the Gombak district of Malaysia. Initially, these caves were used as a shelter by the ancient tribes albeit today there are Hindu temples here.

The most highlighted feature of this temple is 140 feet tall Murugan statue, which is the tallest in the world. The series of caves comprises a Museum Cave and an Art gallery Cave, where both are located at foot of the hill. Here there are different Hindu sculptures and paintings.

Yet Temple Cave is the largest one holding a lot of significance. To reach here, people have to climb 272 steps.

The other small caves involve Ramayana Cave, Hanuman Temple, and Dark Cave.

4 Marble Caves

With the largest marble deposits in the world, these Marble Caves are located along the Chile-Argentina border in South America. It borders Lake General Carrera and the caves have been formed due to the constant erosion of marble for years in General Carrera Lake.

Due to the turquoise blue water as well as the marble glistening in the sunlight, the visual effects of these caves seem unparalleled.

To reach the marble caves, travelers can contact either any travel agency in Puerto Rio Tranquilo and take the boats leaving on General Carrera Lake to the Marble Caves or reach Bahia Mansa, five kilometers south of Puerto Río Tranquilo and find boats or kayaks with cheaper prices to reach the marble caves.

3 Tham Lod Cave, Thailand

Located in Northern Thailand, this is quite renowned worldwide owing to its carvings. These carvings were done by an ancient tribe of Thailand, believed to be the Lawa tribe specifically as the remains of pottery and tools have been traced there.

Nestled deep within the forest, this breathtaking place has murals, ancient coffins, unique rock formations, stalactites, and stalagmites as well as three more connecting caves. Column Cave, Doll Cave, and Coffin Cave are these other caves worth exploring.

A bamboo raft is the best way to explore this cave where one enters through the dark cave via an underground river. To reach the caves, it is 50 km north of Pai town, 180 km from Chiang Mai, and 75 km from Mae Hong Son town.

From Pai town, visitors can either book a tour guide or a cab.

Refrain from visiting the caves during monsoon; November-January is a better timeframe to travel to northern Thailand.

2 Reed Flute Cave, China

A fascinating attraction for thousands of years, Reed Flute Cave has unique limestone formations and multicolored lighting. Located in the Guilin district of China, it derived its name from a type of reed growing outside the caves, which is used to carve melodious flutes.

Initially, the cave is believed to be inhabited by the Tang dynasty owing to the ink inscriptions traced back then. Also known as “Nature’s Art Palace”, this place has formations such as Rose Dawn Over Lion Peaks and “Crystal Palace” which are among the most liked formations.

Note : The cave is merely five kilometers from the city center of Guilin; April to October are the perfect months to visit it.

1 Škocjan Cave

An impressive limestone cave in Slovenia, Škocjan Cave is known for having one of the largest underground chambers. These caves are prime centers for karst topography and thus have, fissures, sinkholes, caverns, collapsed dolines, underground canyons, and streams.

Its appearance seems quite out of the world and is famous for endangered and endemic species. It is listed among UNESCO’s World Cultural and Natural Heritage sites as well.