Halong Bay is formed from 1,969 islands of diverse sizes, 989 islands are given names. There are 2 types of islands, limestone and schist, which are 
concentrated in 2 main zones: the southeast (belonging to Bai Tu Long Bay) and the southwest (belonging to Halong Bay). This densely targeted zone of 
stone islands, world is well-known for its spectacular scenery of grottoes and caves, forms the central sector of Halong Bay that has been named a UNESCO World Heritage site.
The bay itself has an area of 43,400 ha including 775 islands  and forms a triangle with the island of Dau Go (Driftwood Grotto) to the west, the lake of 
Ba Ham (Three Shelter Lake) to the south and the island of Cong Tay to the east.
Viewed the whole sceneries, Halong Bay resembles a geographic work of art. Whereas exploring the Bay, you feel lost in a legendary world of stone islands. There is Man's Head Island that resembles a person standing and searching towards the mainland. Dragon Island feels like a dragon hovering on top of the turquoise water. La Vong Island resembles an old man fishing. There also are the islands of the Sail, the Pair of Roosters, and the Incense Burner, that all astonishingly resemble their namesakes. The varieties of the islands modify based on the angle of the light and from where the islands is viewed. At the core of the islands, there are wonderful caves and grottoes including Thien Cung (Heavenly Residence Grotto), Dau Go (Driftwood Grotto), Sung Sot (Surprise Grotto), and Tam Cung (Three Palace Grotto).
Halong Bay has several links to the history of Vietnam. For instance, Many famous geographical sites as Van Don (site of an ancient business port), 
Poem Mountain (with engravings of many poems concerning emperors and different famous historical figures), and Bach Dang River (the location of 2 fierce naval battles fought against foreign aggressors).
It has been proven by scientists that Halong was one of  the primary cradles of human existence within the sector at such archeological sites as Dong Mang, Xich Tho, Soi Nhu and Thoi Gieng. Furthermore, it's a sector of highly-concentrated biological diversity with several ecosystems of salt water-flooded forests, coral reefs and tropical forests that includes thousands of species of animal and plants.
On the 18th  meeting of the Committee of the World Heritages of UNESCO (in Thailand on December seventeenth, 1994), formally recognized Halong 
Bay as a natural heritage site of worldwide importance.
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