Ha Long Bay is a UNESCO World Heritage Site, and a popular travel destination, in Quang Ninh Province, Vietnam. Administratively, the bay belongs to Ha Long City, Cam Pha town, and part of Van Don District. The bay features thousands of limestone karsts and isles in various sizes and shapes. Ha Long Bay is a center of a larger zone which includes Bai Tu Long bay to the northeast, and Cat Baa islands to the southwest.
Ha Long Bay has an area of around 1,553 km², including 1,960 - 2,000 islets, most of which are limestone. The core of the bay has an area of 334 km² 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, oceanic and sea shore biosystem. Ha Long Bay is home to 14 endemic floral species and 60 endemic faunal species.
Historical research surveys have shown the presence of prehistorical human beings in this area tens of thousands years ago. The successive ancient cultures are the Soi Nhu culture around 18,000 - 7000 BC, the Cai Beo culture 7000 - 5000 BC and the Ha Long culture 5,000 - 3,500 years ago.
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 Ha Long area. French tourists visited in the late 19th century, and named the cave Grotte des Merveilles.
In 2000, the UNESCO's World Heritage Committee has inscribed the Ha Long Bay in the World Heritage List according to its outstanding examples representing major stages of the Earth's history and its original limestone karstic geomorphologic features.