Phia Oac – Phia Den National Park - The northern mountainous province of Cao Bang.
Covering 10,593 hectares, the park spans Thanh Cong, Quang Thanh, Phan Thanh and Hung Dao communes, and Tinh Tuc town in Nguyen Binh district. About 77 percent, or more than 8,146 hectares, of the area is natural forest.
Surveys showed that the park is home to 1,287 types of plants, of which more than 90 are in danger of extinction, and to 496 vertebrate species, including 58 rare types.
The area hosts Phia Oac Mount – one of the three main tourism routes of Non Nuoc Cao Bang Geopark. Non Nuoc Cao Bang was the second UNESCO-recognised Global Geopark in Vietnam after Dong Van Karst Plateau.
The park is designated to ensure environmental security and mitigate land erosion and floods, thus helping to stabilise production and improve livelihoods of local people in downstream regions. To protect the national park, the local authorities have set up forest ranger units and forest monitoring groups in villages. 
Scientific research and activities will be held to preserve and develop endangered genetic sources, rescue wildlife animals and raise public awareness of the protection of environment and biodiversity.