Last month, a trio of British divers ventured to Phong Nha-Ke Bang National Park to explore the cave's waterways (Photo: CNN)

 

During the groundbreaking dive, they discovered a new underwater tunnel that connects Son Doong with another enormous cave called Hang Thung (Photo: CNN)

 

Son Doong currently measures a total of 38.5 million cubic meters. When it's officially connected with Thung Cave, it will add an additional 1.6 million cubic meters in volume (Photo: CNN)

 

One of the world's most precious natural wonders, Son Doong was inadvertently discovered by Vietnam resident Ho Khanh in 1990 (Photo: CNN)

 

It was first explored in 2009 by the British Cave Research Association and has been open to the public since 2013 (Photo: VNA)

 

Son Doong Cave has been recognised as the largest of its kind in the world by three international record-keeping organisations – Guinness, the Association World, and WorldKings (Photo: VNA)

 

The 1,645m-long cave system, which extends through a mountain, was named one of the most captivating caves on earth by National Geographic (Photo: VNA)

VNA