The Cat Ba Archipelago shares the distinctive rugged appearance and scenic beauty of the Halong Bay Area that was declared a UNESCO World Natural Heritage Site, in 1994. The area is one of the best examples in the world of a Karst landscape invaded by the sea. Some 1,00-2,000 large and small islands and cliffs rise steeply from the shallow marine waters.
Many of these islands reach towering heights from 50 to 100m with sheer vertical cliffs on all sides. Spectacular rock relief and bizarre rock formations provide evidence of a long history of erosion and landscape evolution through the sculpturing power of water. The greatest part of the islands' mountain range like most of the smaller offshore islands of the Archipelago, are covered by tropical moist limestone forest. Cat Ba Island also has coral terraces, sandy beaches, freshwater wetland areas, tidal flats, mangrove forests and willow swamps. Spectacular scenery and a high diversity of landscapes make Cat Ba a special place and it has become a main destination for national and international tourists.
Cat Ba is the largest among the total number of 1969 islands of Halong Bay. This is a beautiful and romantic island at 70m above the sea level. The island is home to the Cat Ba town which overlooks the Lan Ha gulf and 6 communes of Gia Luan, Hien Hao, Phu Long, Tran Chau, Viet Hai, Xuan Dam with around 13,500 inhabitants.
Cat Ba National Park was established in 1986. After a re-arrangement of the park boundaries in 2006, the park now comprises of 109 square km of land area and an additional 52 square km of inshore waters and mangrove covered tidal zones. Cat Ba National Park was Vietnam's first national park to include both terrestrial and marine ecosystems.
Cat Ba Island, its national park and the surrounding area are nationally and internationally recognized for their importance to biodiversity conservation, exemplified through the recognition of the Cat Ba Archipelago as a UNESCO Man and Biosphere Reserve, in 2004. This is not only because the area has a high number of different ecosystem and habitat types, but also because it possesses a great variety of plant and animal species, many of which, like the Cat Ba langur, are now rare and endangered.
About 1,400 vascular plants, including 23 Endangered and Critically Endangered species (Red Data Book of Vietnam; IUCN Red List) have so far been recorded. Large and partly endangered mammals include the Cat Ba langur, the Southern Serow (Naemorhaedus sumatraensis), Rhesus macaque (Macaca mulatta), Leopard Cat (Prionailurus bengalensis), black giant squirrel (Ratufa bicolor), and civet cats (Viverricula indica, Paradoxurus hermaphroditus). The cave, land snail and butterfly fauna are rich including the most northerly cave-adapted crab species, plus four species of true cave snails. The region is considered a hotspot for land snail diversity and might also be conserving a considerable number of bat species including rare ones.