Hạ Long Bay is located in northeastern Vietnam, from E106°56' to E107°37' and from N20°43' to N21°09'. The bay stretches from Yên Hưng district, past Hạ Long city, Cẩm Phả town to Vân Đồn district, bordered on the south and southeast by the Gulf of Tonkin, on the north by China, and on the west and southwest by Cát Bà island. The bay has a 120 km long coastline and is approximately 1,553 km² in size with about 2000 islets. The area designated by UNESCO as the World Natural Heritage Site incorporates 434 km² with 775 islets, of which the core zone is delimited by 69 points: Đầu Gỗ island on the west, Ba Hầm lake on the south and Cống Tây island on the east. The protected area is from the Cái Dăm petrol store to Quang Hanh commune, Cẩm Phả town and the surrounding zone.
Halong bay Climate
The climate of the bay is tropical, wet, sea islands, with two seasons: hot and moist summer, and, dry and cold winter. The average temperature is from 15°C- 25°C, and annual rainfall is between 2000mm and 2200mm. Hạ Long Bay has the typical diurnal tide system (tide amplitude ranges from 3.5-4m). The salinity is from 31 to 34.5MT in the dry season and lower in the rainy season.
Halong bay History
Soi Nhụ culture (16,000- 5000 BC)
Located in Hạ Long and Bái Tử Long are archaeological sites such as Mê Cung and Thiên Long. There are remains from mounds of mountain shellfish (Cyclophorus), spring shellfish (Melania), some fresh water mollusk and some rudimentary labour tools. The main way of life of Soi Nhụ's inhabitants included catching fish and shellfish, collecting fruits and digging for bulbs and roots. Their living environment was a coastal area unlike other Vietnamese cultures, for example, like those found in Hoà Bình and Bắc Sơn.
Cái Bèo culture (5000- 3000 BC)
Located in Hạ Long and Cát Bà island, its inhabitants developed to the level of sea exploitation.
History shows that Hạ Long Bay was the setting for local naval battles against Vietnam's coastal neighbors. On three occasions, in the labyrinth of channels in Bach Dang river near the islands, the Vietnamese army stopped the Chinese from landing. In 1288, General Tran Hung Dao stopped Mongol ships from sailing up the nearby Bach Dang River by placing steel-tipped wooden stakes at high tide, sinking the Mongol Kublai Khan's fleet.
During the Vietnam War, many of the channels between the islands were heavily mined by the United States navy, some of which pose a threat to shipping to this day.