A popular coastal destination in northeastern Viet Nam, Ha Long Bay features many tropical plants and animals, floating fishing villages, and unique formations of eroded limestone, including a multitude of small islands and huge caves.

Ha Long Bay has an area of around 1,550 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