Dark cave is an adventurous and action-packed experience. Visiting this cave includes harnessed zip lining over a turquoise river, swimming into the mouth of the cave (life jackets included), walking through the dark with only the head torch on your mining helmet to illuminate the way, having a mud fight in the buoyant mud baths deep in the cave, washing clean with a swim in the lake inside the cave, then kayaking back across the river to test your strength on the hanging obstacle course and open ziplines.
Phong Nha Cave is not only a natural legacy of the world. It also stands as a relic system of the historic Ho Chi Minh trail which, during the US war, served as a secret hiding place for floating bridges that were only brought out at night to avoid targeted bombings. These bridges were key components in the supply chain from the north to the south by allowing supply trucks to cross the rivers. It also once served as a hospital, with weapons installed at the entrance.