This summer, I had a chance to visit Vietnam. My objective for this visit was an expedition tour of Son Doong Cave.

For those who might be interested in Son Doong Cave, I’ve got an overview from Wikipedia.

Sơn Đoòng Cave is in Phong Nha-Kẻ Bàng National Park, Bố Trạch District, Quảng Bình Province, Vietnam.
Located near the Laos–Vietnam border, Hang Sơn Đoòng has an internal, fast-flowing subterranean river and the largest cross-section of any cave, worldwide, as of 2009, believed to be twice that of the next largest passage. It is the largest known cave passage in the world by volume.
Its name, Hang Sơn Đoòng, is variously translated from Vietnamese as ‘cave of the mountain river’ or ‘mountain cave of Đoòng’.
As a solutional cave, it was formed in soluble limestone and is believed to be between 2 and 5 million years old.

https://en.wikipedia.org/wiki/Hang_Sơn_Đoòng

This video was filmed during the 5 Days 4 Nights Expedition tour provided by Oxalis Adventure Tours.