Cu Chi Tunnels top the world's most implicit underground destination

The interlocking tunnel system of more than 320 km long, full of works serving the life of the war in South Vietnam, shocked the international tourists.

Cu Chi Tunnels, Vietnam : This unique attraction is located more than 30 km from Ho Chi Minh City, built during the war against France.(Photo: Lesrivesexperience.)

The complex tunnel system over 300 km long has enough living places, hospitals, supply lines and warehouses to serve life in the war.The former narrow entrance, hidden under the carpet of fallen leaves, is now expanded so visitors can explore inside.(Photo: Visa2vietnam.)

Catacombs of Paris, France : This is the place where the remains of more than 6 million people died in the period of 1785-1860.This bone is separated and arranged into corridors, doors, columns . (Photo: Smithsonianmag).

The network of more than 300 km long consists of ancient caves, tunnels and deep holes, mostly filled with human bones.The tourists often come here to visit during the day.However, the tomb has a room for two travelers who are brave enough to spend the night here.(Photo: CNN.)

Bounce Below, Llechwedd, Wales mine : The world's largest trampoline is located in a giant cave at Llechwedd mine, Blaenau Ffestiniog, with 3 large trampoline to delight guests(Photo: Thisiscolossal.)

You can go to Bounce Below by train.However, each spring is located next to an 18m-long slide that floats on the deep, not for those who are afraid of heights.(Photo: CNN).

Salina Turda, Romania : This underground amusement park is located in one of the oldest salt mines in Romania.These mines are excavated by the medieval people to exploit salt.(Photo: Businessinsider.)

Now the Salina Turda mine is turned into an amusement park with a round of wooden horses, ferris wheel, theater, bowling alley, mini golf course and underground lake.(Photo: Cartitaplimbareata).

Boongke Cabinet War, London, England: The late President Churchill ran the politicians from the Boongke during World War II, staying here overnight when advisers assumed that returning to 10 Downing Street was too dangerous.(Photo: Amylaughinghouse.)

These rooms account for only one-third of the 3,000-square-foot underground complex used in 1940-1945.Currently, this place still maintains many interesting historical artifacts.(Photo: Sightseeingtours.)

Coober Pedy, Australia : Here, visitors will discover underground life, where more than 3,500 residents have built houses and many shops under the clay rock of the Outback.(Photo: Dailymail).

This underground town has houses, churches, museums, galleries, restaurants, bars, and even hotels for those who want to stay overnight.The house here is fully equipped, from wall cabinets, fireplaces, kitchens.(Photo: Urbanpeek).

Salt church, Colombia : Located at a depth of 180 m above the ground, this church is a feat, with statues carved from salt and a huge cross between the center.(Photo: Famouswonders).

It is now an attractive attraction, located in Nemocon, Cundinamarca, more than 90 km from Bogata.This mine has existed 500 years ago, currently welcomes about 3,000 visitors every Sunday.(Photo: Paradiseintheworld.)

Wieliczka salt mine, Poland : Wieliczka salt mine is Poland's largest attraction, with hundreds of kilometers of tunnel.A nursing home located deep underground here is favored by asthma patients, thanks to pure air.(Photo: Thedailybeast.)

In addition, there is a chapel, a ballroom, a restaurant, a shop . All of them are made from monoliths.(Photo: Grupafuntime).

The Vaults, London, England : The Vaults hosts a variety of theater shows, movies, golf and night events.(Photo: Hirespace.)

Deep in the tunnel under Waterloo Station, The Vaults Theater has 176 seats with classic, mysterious atmosphere.There is also a gallery and kitchen for visitors.(Photo: Vaultsbirmingham.)