Reed Flute Cave

Forgotten for 1,000 years, the Reed Flute Cave in China was discovered by Japanese refugees during World War II. According to the research of Chinese scientists, the approximate age of the cave is over 180 million years. In one of the halls, there is a suspension bridge over a small lake.

Longyou Grotto

Discovered on accident by a local Chinese villager in 1992, the Longyou Grottoes are dated back at least 2,000 years. It is a series of 24 underground man-made caves not communicating with each other. The average area of each room is more than a thousand square meters, and the height is up to 30 meters. How they were constructed still remains a mystery.

Puerto Princesa Underground River

The world's longest underground navigable river, the Puerto Princesa Underground River is located in the Philippines under the island of Palawan. The Puerto Princesa flows in a huge cave 8 km long. In the depths of the cave there is a lack of oxygen. Tourist routes are limited to 1-2 km, this is enough to enjoy stalactites and stalagmites.

Ozarks Caverns

The Ozarks State Park in Missouri is home to many amazing caves and caverns, thanks to a natural drainage system.

Greenbrier Bunker

President Eisenhower worried about running the country during a potential nuclear war. So, they build the Greenbrier Bunker for Congress in the event of an attack. The place is located under the Greenbrier luxury hotel in Virginia, the USA. The structure has an impressive scale: transport underground parking, water storage tanks, radio broadcasting center, medical offices, conference rooms, a library, a sports hall, etc.

The bunker was never used and is now a beautiful relic of the past and a popular tourist attraction.

Škocjan Caves

Located in Slovenia, the Škocjan Caves is a system of tunnels and halls that cover the area of 6 km under the ground, In this territory, there are many karst dips and funnels, as well as dozens of small waterfalls. The caves have one of the largest underground chambers.

Coober Pedy

Coober Pedy is an underground city located right in the middle of Australia, thousands of miles away from Australia's capital city. The name of the city from the language of Australian Aborigines translates as "the burrow of a white man". The city was built in empty mines where opal was produced. Underground apartments have become a necessary measure for workers and their families, where they could hide from the burning heat. The air temperature on the surface often exceeds 50 degrees.

Les Catacombes de Paris

Derinkuyu Underground City

Derinkuyu Underground City is an ancient and complex underground city underneath modern-day Turkey. The tunnels are full of dwellings and homes and could house up to 20,000 people if they needed to. The city reaches around 76 m deep. Built in the 2-1 millennium BC, it was discovered in 1936.

Cave of Crystals

Located in Chihuahua, Mexico, the Cave of Crystals is definitely a sight to behold. The cave is at a depth of 300 meters below the ground and has some of the largest natural crystals in the world. The largest of the crystals found is 11 meters long and 4 meters wide with a weight of 55 tons. Unfortunately, due to the hot magma underneath the cave, it's mostly too hot and humid to explore fully.

Củ Chi Tunnels

Built during the Vietnam War, the Củ Chi Tunnels are extensive interconnected tunnels that were used the tunnels for their guerrilla warfare tactics. Tunnels stretch for about 150 km. Labyrinths included secret passages, living quarters, warehouses, and hospitals.

Dambulla Cave Temple

The Dambulla Cave Temple located at the center of Sri Lanka with 153 Buddhist statues as well as statues of Hindu gods and Sri Lankan kings is a main tourist attraction. he temple has been a sacred place of pilgrimage for already 22 centuries. Many of the carvings and statues are still very well preserved, which is impressive considering it dates back to the third century BCE.