Cu Chi Tunnels are among the world's most unusual underground destinations.

The intricate tunnel system, stretching over 320 km and complete with facilities serving life during the war in South Vietnam, has astonished international tourists.

Cu Chi Tunnels, Vietnam:This unique attraction is located more than 30 km from Ho Chi Minh City and was built during Vietnam's resistance war against the French. Photo: Lesrivesexperience.

The complex tunnel system, stretching over 300 km, contained living quarters, hospitals, supply lines, and warehouses to support life during wartime. The previously narrow entrance, hidden beneath a carpet of fallen leaves, has now been widened to allow visitors to explore the interior. Photo: Visa2vietnam.

The catacombs of Paris, France:This is where the remains of over 6 million people who died between 1785 and 1860 are kept. The bones are separated and arranged into corridors, doorways, columns, etc. (Photo: Smithsonianmag)

The network, stretching over 300 km, comprises numerous ancient caves, tunnels, and caverns, most of which are filled with human bones. Visitors typically come here during the day. However, the catacombs have rooms designed for two visitors brave enough to spend the night.

Bounce Below, Llechwedd oil field, North Wales:The world's largest trampoline park is located in a giant cave in the Llechwedd mine, Blaenau Ffestiniog, featuring three large trampolines for visitors to enjoy. Photo: Thisiscolossal.

You can get to Bounce Below by train. However, each trampoline is located next to an 18-meter-long slide suspended over a deep ravine. Therefore, it's not for those afraid of heights. Photo: CNN.

Salina Turda, Romania:This underground amusement park is located in one of the world's oldest salt mines in Romania. These mines were dug by medieval people to extract salt. Photo: Businessinsider.

The Salina Turda mine has now been transformed into an amusement park featuring a carousel, theater, bowling alley, mini-golf course, and underground lake. Photo: Cartitaplimbareata.

Cabinet War Bunker, London, England:Former President Churchill led politicians from this bunker during World War II, staying here overnight when advisers deemed it too dangerous to return to 10 Downing Street. Photo: Amylaughinghouse.

These rooms occupy only one-third of the 3,000 square meter underground complex used in 1940-1945. Today, it still houses many interesting historical artifacts. Photo: Sightseeingtours.

Coober Pedy, Australia:Here, visitors can explore life underground, where more than 3,500 residents have built their homes and numerous shops beneath the clay bedrock of the Outback. Photo: Dailymail.

This underground town has houses, a church, a museum, an art gallery, restaurants, bars, and even a hotel for those who want to stay overnight. The houses here are fully equipped with amenities, from built-in wardrobes and fireplaces to kitchens. (Photo: Urbanpeek)

Salt Church, Colombia:Located 180 meters below ground, this church is a marvel, featuring statues carved from salt and a giant cross in its center. Photo: Famouswonders.

This place is now a popular tourist attraction, located in Nemocon, Cundinamarca, more than 90 km from the capital Bogota. The mine, dating back 500 years, currently welcomes around 3,000 visitors every Sunday. Photo: Paradiseintheworld.

Wieliczka Salt Mine, Poland:The Wieliczka Salt Mine is Poland's largest tourist attraction, with hundreds of kilometers of tunnels. A sanatorium located deep underground is popular with asthma patients due to its pure, unpolluted air. Photo: Thedailybeast.

In addition, the place also features a chapel, ballroom, restaurant, shops, and more, all carved from solid blocks of salt rock. Photo: Grupafuntime.

The Vaults area, London, England:The Vaults hosts numerous theatrical performances, film screenings, golf games, and evening events. Photo: Hirespace.

Located deep within the tunnels beneath Waterloo Station, The Vaults Theatre has 176 seats and a classic, mysterious atmosphere. It also features an art gallery and a kitchen for visitors. Photo: Vaultsbirmingham.

Located deep within the tunnels beneath Waterloo Station, The Vaults Theatre has 176 seats and a classic, mysterious atmosphere. It also features an art gallery and a kitchen for visitors. Photo: Vaultsbirmingham.

According to Zing.vn