Dark Cave (Hang Toi)

Dark Cave (Hang Toi) is a natural cave attraction in Phong Nha-Ke Bang National Park, Son Trach Commune, Bo Trach District, Quang Tri Province. Located on the Chay River, it is known for its unlit interior preserved in natural darkness and its adventure-based visitor experience. The site combines cave exploration with zipline, kayaking and mud bathing activities, and forms part of the UNESCO World Heritage-listed Phong Nha-Ke Bang karst landscape.

Visitors access Dark Cave via a zipline over the Chay River or by kayak, then enter the cave with helmet and headlamp as there is no artificial lighting inside. Inside, the cave is dark and features natural mud pools where visitors can bathe, narrow passages and stalactite formations. Outside, visitors can kayak and swim in the Chay River, enjoy the surrounding jungle and limestone karst scenery of Phong Nha-Ke Bang National Park. The experience is guided and adventure-oriented.

Dark Cave is part of the Phong Nha-Ke Bang National Park, inscribed as a UNESCO World Heritage Site in 2003 for its geological and geomorphologic values. The park's karst system formed over 400 million years ago and contains one of the world's most extensive cave systems. Dark Cave is preserved without artificial lighting to maintain its natural state.