The name Ba Be means "three lakes", although the lake is one continuous water body, 8 km long and up to 800 m wide. At an altitude of 178 m, Ba Be is the only significant natural mountain lake in Vietnam. It is up to 29 m deep, and contains numerous small limestone islets. The site ranges in altitude from 150 to 1,098 m.
Phong Nha-Ke Bang National Park is located in western Bo Trach district, close to the international border with Laos. The national park is situated in one of the largest areas of contiguous limestone karst in Indochina, which also includes HinNamno National Protected Area in Laos. The limestone massif is located in a transitional zone between the northern and central Annamite mountains.
Cat Ba National Parkis located in Cat Hai district, Hai Phong city. The national park is centered on Cat Ba island, a 28,500 ha island, which lies 20 km due east of Hai Phong city and immediately to the west of Ha Long bay. The national park also incorporates some of the small islands and marine waters situated to the east of Cat Ba island.