In Ha Long Bay, in Quảng Ninh province, in northeastern Vietnam

 "Hạ Long Bay is a geological wonder, made up of 1,600 islands and islets, most of which are uninhabited...." -– David Shukman

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(in Quảng Ninh province, in northeastern Vietnam) Hạ Long Bay is a UNESCO World Heritage Site and popular travel destination. (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 climate, and cultural characters.

+ The core of Hạ Long Bay has an area of 334 km2 (129 sq. mi.) 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 BCE, the Cái Bèo culture 7,000–5,000 BCE 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.
In 1962, the Ministry of Culture, Sports and Tourism of North Vietnam listed Hạ Long Bay in the National Relics and Landscapes publication. Before the 19th century, the name Hạ Long Bay had not been recorded in the old books of the country. In the late 19th century, the name Hạ Long Bay appeared on the Maritime Map of France.

+ 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)