UNDERGROUND RIVER

There is an underground river inside Hang Son Doong Cave which is a combination of the water coming from En Cave and Khe Ry Cave (the longest underground river cave where the water comes from the Vietnam/Laos border area). From Son Doong entrance, you have to cross knee–deep rivers twice to reach the Hope and Vision Passage. There are emergency bridges in case of high water levels. The small waterfalls along the way create loud rumbles. Sometimes, the cave is filled with mist. This underground river disappears near Doline 1, about 4.5km away from the cave entrance. You can learn more about the underground river inside Hang Son Doong Cave here.

FOSSIL PASSAGE

Located next to the underground river at a depth of 40m below the campsite - Doline 1. This passage is imprinted with corals which have been fossilised hundreds of million years ago. This passage also has a 17 to 20 degrees Celsius underground lake in which visitors can swim and relax after a long hard trekking day. For safety reasons, life jackets and headlamps are required. Most visitors said that swimming in this cold underground lake is one of the best experiences that should not be missed in the Son Doong Expedition. You can read more about the Fossil passage here.

DOLINE 1 - WATCH OUT DINOSAUR

The collapsed ceiling of Son Doong formed a big opening to the outside, called Doline 1 (or skylight). Approximately 450 m high from the top to the bottom. This is also where the underground river disappears. On sunny days, there will be giant sunbeams coming in (from about 11 am to 1 pm), especially from January to March every year. Due to the solar orbit, the sunbeams shine deep inside the cave, illuminating the large passages. The beam from above the sky and the mist from the underground river create a majestic scene that can not be found elsewhere. Google Doodle has displayed this magnificent moment in Son Doong Cave on its search homepage. Many people said that it is like another planet, while others thought it was like the movie Avatar. Please learn more about Doline 1- Watch out for Dinosaurs here.