In Deep: Vietnam’s Ha Long Bay, 500 Million Years in the Making

 Now a UNESCO World Heritage Site, Ha Long Bay is located in Northeastern Vietnam, 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. Famous worldwide for its stunning limestone karsts and isles in various sizes and shapes, the bay has an area of around 1,500 square kilometres including 1,960 islets, most of which are limestone.

The bay’s limestone has gone through 500 million years of formation in different conditions and environments; by comparison, its karst has developed over a mere 20 million years under the impact of the wet, tropical climate. The diversity of the environment, climate, geology, geography and geomorphology in the area has created a noted biodiversity, but its sheer beauty is what makes it recognized as one of the most beautiful bays of the world.

The bay consists of a dense cluster of limestone monolithic islands, each topped with thick jungle vegetation, which rise spectacularly from the ocean. Several of the islands are hollow, with enormous caves. Hang Đầu Gỗ, the Wooden Stakes Cave, is the largest grotto in the Ha Long area. Its three large chambers contain large numerous stalactites and stalagmites.

Two large islands, Tu on Châu and Cat Ba, have permanent inhabitants, but most of the inhabitants in the bay reside in four floating villages. This population of roughly 1,600 people (a tiny fraction of Vietnam’s total population of nearly 88 million) lives in floating houses and sustains itself through fishing and marine aquaculture.

Did You Know?

History shows that Ha Long Bay was the setting for ancient naval battles against Vietnam’s coastal neighbours to the north. On three occasions, in the labyrinth of channels in Bach Dang river east of Cát Bà Island, the Vietnamese stopped the Chinese from landing. More famously, in 1288, General Tran Hung Dao stopped Mongol ships from sailing up the river by placing steel-tipped wooden stakes at high tide and sinking the Mongol Kublai Khan’s fleet, preventing the seemingly invincible Mongols from invading Vietnam.

Preserving Natural Beauty

Ha Long Bay was first listed as a UNESCO World Heritage Site in 1994, and with the opening up of Vietnam during that decade, tourism became important to the livelihood of the locals here. However, with an increased number of tourists now visiting Hạ Long, the bay has suffered. The natural mangroves and seagrass beds have had to be cleared, and jetties and wharves have been built for tourist boats. Fuel and oil, along with tourist litter, have created pollution problems, which have had a negative impact on both the aquatic and terrestrial ecosystem of the islands.

Ha Long Bay remains one of the most spectacular sites on earth, but will have to find a way to preserve not only its natural beauty, but also the ecosystem that draws thousands to Vietnam each year and makes it one of the great tourist destinations in the world. 

See Vietnam Your Way

From sleepy fishing villages to the flurry of activity in its big cities, Vietnam is a country with a rapidly developing future. Discover the best of the country on a Bespoke Vietnam adventure. After two decades here, we’ve found our favourite spots, from pristine beaches to lush mountains…and made incredible friendships along the way. Slow down to see Vietnam…choose your own adventure.


Cát Bà Island

To the south of the city of Halong sits the 140 square kilometre island of Cát Bà, the largest island in Halong Bay. Marked by amazing limestone formations and a high biodiversity, Cát Bà has become an increasingly important tourist destination in Vietnam. Traditionally, its nearly 8,000 inhabitants relied on pearl farming or shrimp farming, but increasingly, the locals are discovering tourism as a major industry—especially since approximately half of the island is covered by a National Park.

Cát Bà Langur

The highly endangered golden-headed Cát Bà langur exists only on the Cát Bà Island, and there are fewer than 100 alive today. The species is one of the most endangered primates in the world; its population diminished to 53 individuals in 2000. Poached for the preparation of traditional medicine known as “monkey balm,” the animal is only rarely caught for food, as their meat has a very unpleasant smell.

Scientists believe that the Cát Bà langur immigrated to the island long before the sea level rose from melting glacial ice, and that they have lived here for some 10,000 years. The langur lives in limestone forests and sleeps in as many as 12 different resting caves over the course of a year.

The daily life of a Cát Bà langur is devoted to foraging and resting, and its diet consists mainly of leaves, fresh shoots, flowers, bark and some fruits that are not palatable to human beings.

The good news is that with all the attention on tourism, there seems to be a well-organized conservation program under way, with a conscientious effort to preserve the langur’s existence. UNESCO recognized the island as a World Biosphere Reserve in 2004.

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