Quang Binh Province borders Ha Tinh Province on the north with the Ngang mountain pass as the natural frontier, Quảng Trị province to the south, Laos to the west, and faces the Dong Sea to the east. The narrowest part from east (seaside) to west (Laotian border) is just 40 km. The provincial topography is characterized by a general slope, higher in the west and lower in the east, with hilly and mountainous areas accounting for 85% of the total area. The Annamite Range is the natural border between Quang Binh province and Laos with peaks ranging from 1,000 to 1,500 m, the summit of which is peak Phi Co Pi with the height of 2,017 m. In the east of the province are lower hills and then several narrow plains and river deltas. The seaside sand dunes belt is a natural dam that protects the land from the ocean tides.
The provincial land area is 8,037.9 km2 and divided as follows:
- Inhabited land: 41.45 km2
- Agriculture: 1635.46 km2
- Forest: 4912.62 km2
- Specific usage: 199.36 km2
- Unused: 26.01 km2
Sand area accounts for 5.9% of the land, and alluvial soil accounts for only 2.8% of the land. The province’s east coastline is 116.04 km long and the western borderline with Laos is 201.81 km long. The province owns 4866.88 km2 of forests, of which 4478.37 km2 is natural jungle, and 388.54 km2 is reforestation (including 175.97 km2 of pines).
The Phong Nha National Park, famous for its magnificent grottoes, is reached from the sea resort of Dong Hoi (Province of Quang Binh) 488 km south of Hanoi (170 km north of Hue. There are 4 grottoes : the Phong Nha Grotto, 30 km from Dong Hoi, the largest in the world, a complex of grottoes and caverns, of which 55 km have been explored, but it is probably over 70-km long ; the Tien Son Grotto, in a mountain above Phong Nha ; the Paradise Grotto, 60 km from Dong Hoi and 31-km long, and the Son Duong Grotto, discovered in 2009 and containing the largest cavern in the world : 5-km long, 200-m high and 150-m wide. Only the first 3 can be visited.
The Phong Nha Grotto is located near the small village of Son Trach. From the village, a boat takes the visitors to the entrance and then enters the grotto. The visit lasts 2 hours.
The Tien Son Grotto, a dry grotto in a mountain above Phong Nha, is accessible with 330 steps. It shelters vestiges of Cham shrines and inscriptions dating IXth century. 1-hour visit.
The Paradise Grotto (Thien Duong)was discovered in 2005 and open to the public in 2011, it is supposed to be the longest dry grotto in the world. Electrical carts (or 500 steps) lead you to the entrance. Its dimensions are breathtaking, with colossal stalagmites and crystal stalactites resembling glass columns. Small restaurant adjacent to the Welcome Center and café at the entrance of the grotto.