Considering the overall dimensions, Hang Son Doong Grotto (Mountain River Cave) is the largest underground gallery in the world.
Not surprisingly, the cave is cathedral-like: it is about 200 meters high, 150 meters wide and at least 6.5 kilometers long. To get an idea of these dimensions, at its highest point the cave is twice as tall as the Statue of Liberty.
Vietnam
Hang Son Doong Grotto is located in Phong Nha-Ke Bang National Park, in Quang Binh Province, Vietnam. And its interior can only be accessed by abseiling.

The cave was discovered in 1991 by Ho Khanh , a farmer in the area. However, it took another 18 years for him to retrace his steps and locate her again.
In April 2009, he led a team of British spelunkers on a six-hour excursion through the jungle to Hang Son Doong, managing to make a partial inspection of the cave.
With its enormous dimensions, Sơn Đoòng surpasses the Deer Cavern of the Gunung Mulu National Park in Malaysia, thus taking the title of the largest cavern in the world.