The Dark Cave or Hang Toi in Vietnamese is located in Bo Trach District, Quang Binh Province, about 50 kilometers to the northwest of Dong Hoi City. This is the only cave in Vietnam where you can enjoy mud-bathing spa.
Located in the core area of Phong Nha Ke Bang National Park, on the bank of Chay River, the Dark Cave typifies geological tectonics of 400-500 million years ago. Explored and named by the British Caving Association in 1992, the cave has length of 5,558m, width of 50m, height of 80m and includes front entrance (adjacent to Chay River) and back entrance (next to the forest).
The cave has many kinds of stalactites with abundant colors and shapes. In particular, some rare stalactites with parasitic fern are vestige of geology in strong motion period. The geologists also explored the underground sections of the river in Dark Cave as well as a natural freshwater lake named Thuy Tien and a 20m2 mud lake containing vital minerals for health.
Dark Cave area is home to several animal species such as bat, swallow, especially Ha Tinh langur is one of the primate species in Vietnam’s Red List.
Currently, many travel activities are offered by the Tourism Center of Phong Nha Ke Bang. From the observation tower, visitors can experience 400m long zip-line service crossing the Chay River to the front entrance of Dark Cave, mud-bathing in the cave, kayaking on the river and take part in some other water activities.