Son Doong Cave, a cave belongs to the Phong Nha-Ke Bang grotto system in central Quang Binh Province, has been discovered to be the biggest in the world.

Son Doong cave, discovered by a local 18 years ago, is more than 200 meters wide, 150 meters high, and at least 6.5 kilometers long, though the explorers said they were unable to explore it fully. Bristish explorers have recently discovered that So Dong is much larger than the world's biggest known cave. The biggest section of Son Dong is five kilometers in length, 200 meters high and 150 meters wide, said Howard Limbirt of the British Cave Research Association team searching the area April 10-14, 2009. Son Dong is much larger than Deer Cave in Malaysia, currently considered the world's largest, an explorer said (Deer is 90 meters wide, 100 meters high and 2 kilometers long). The Son Doong cave has replaced to take pole position as the world's largest cave.