Hạ Long Bay or Halong Bay (, ) is a UNESCO World Heritage Site and popular travel destination in Quảng Ninh province, Vietnam. The name Hạ Long means "descending dragon". Administratively, the bay belongs to Hạ Long city, Cẩm Phả city, and is a part of Vân Đồn district. The bay features thousands of limestone karsts and islets in various shapes and sizes. Hạ Long Bay is a center of a larger zone that includes Bai Tu Long Bay to the northeast, and Cát Bà Island to the southwest. These larger zones share a similar geological, geographical, geomorphological, climate, and cultural characters.
Hạ Long Bay has an area of around , including 1,960–2,000 islets, most of which are limestone. The core of the bay has an area of with a high density of 775 islets. The limestone in this bay has gone through 500 million years of formation in different conditions and environments. The evolution of the karst in this bay has taken 20 million years under the impact of the tropical wet climate. The geo-diversity of the environment in the area has created biodiversity, including a tropical evergreen biosystem and a seashore biosystem. Hạ Long Bay is home to 14 endemic floral species and 60 endemic faunal species.

Historical research surveys have shown the presence of prehistoric human beings in this area tens of thousands years ago. The successive ancient cultures are the Soi Nhụ culture around 18,000–7,000 BC, the Cái Bèo culture 7,000–5,000 BC and the Hạ Long culture 5,000–3,500 years ago. Hạ Long Bay also marked some important events in Vietnamese history, with many artifacts found in Bài Thơ mountain, Đầu Gỗ cave, and Bãi Cháy.

Nguyễn Trãi praised the beauty of Hạ Long Bay 500 years ago in his verse , in which he called it "a rock wonder in the sky". In 1962, the Ministry of Culture, Sports and Tourism of North Vietnam listed Hạ Long Bay in the National Relics and Landscapes publication. In 1994, the core zone of Hạ Long Bay was listed as a World Heritage Site under Criterion VII, and was listed for a second time under Criterion VIII.

Etymology
The name Hạ Long (chữ Hán: 下龍) means "descending dragon".
Before the 19th century, the name Hạ Long Bay had not been recorded in the old books of the country. It has been called An Bang, Lục Thủy, Vân Đồn ... In the late 19th century, the name Hạ Long Bay appeared on the Maritime Map of France. The French-language Hai Phong News reported "Dragon appears on Hạ Long Bay".
According to local legend, when Vietnam had just started to develop into a country, they had to fight against invaders. To assist the Vietnamese in defending their country, the gods sent a family of dragons as protectors. This family of dragons began spitting out jewels and jade. These jewels turned into the islands and islets dotting the bay, linking together to form a great wall against the invaders. Under magics, numerous rock mountains abruptly appeared on the sea, ahead of invaders' ships; the forward ships struck the rocks and each other. After winning the battle, the dragons were interested in peaceful sightseeing of the Earth, and then decided to live in this bay. The place where the mother dragon descended was named Hạ Long, the place where the dragon's children attended upon their mother was called Bái Tử Long island (Bái: attend upon, Tử: children, Long: dragon), and the place where the dragon's children wriggled their tails violently was called Bạch Long Vĩ island (Bạch: white-color of the foam made when Dragon's children wriggled, Long: dragon, Vĩ: tail), present-day Tra Co peninsula, Móng Cái.
Overview
The bay consists of a dense cluster of some 1,600 limestone monolithic islands each topped with thick jungle vegetation, rising spectacularly from the ocean. Several of the islands are hollow, with enormous caves. Hang Dau Go (Wooden Stakes cave) is the largest grotto in the Hạ Long area. French tourists visited in the late 19th century, and named the cave Grotte des Merveilles. Its three large chambers contain large numerous stalactites and stalagmites (as well as 19th-century French graffiti). There are two bigger islands, Tuần Châu and Cát Bà, that have permanent inhabitants, as well as tourist facilities including hotels and beaches. There are a number of beautiful beaches on the smaller islands.





