Hạ Long Bay, also called Halong Bay (Vietnamese: Vịnh Hạ Long, pronounced [vînˀ hâːˀ lawŋm]), is a bay in northeastern Vietnam. The name "Hạ Long" means "descending dragon." The bay is managed by the cities of Hạ Long and Cẩm Phả in Quảng Ninh province. It is known for thousands of limestone rock formations and islands of different shapes and sizes. These features earned it a place on the UNESCO World Heritage List and made it a popular tourist destination. The bay is part of a larger area that includes Bai Tu Long Bay to the northeast and Cát Bà Island to the southwest. These areas share similar geological, geographical, and environmental features.

Hạ Long Bay covers an area of about 1,553 square kilometers (600 square miles), including 1,969 islands, most of which are made of limestone. The central part of the bay has an area of 334 square kilometers (129 square miles) and contains 775 islands. The limestone in this region formed over 500 million years in different environments. The development of the karst landscape took 20 million years due to the tropical wet climate. The area's diverse environment supports different ecosystems, including a tropical evergreen forest system and a coastal system. Hạ Long Bay is home to 14 plant species and 60 animal species found nowhere else in the world.

Historical research shows that humans lived in this area tens of thousands of years ago. Ancient cultures include the Soi Nhụ culture (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). Important events in Vietnamese history are linked to Hạ Long Bay, with artifacts discovered in locations like Bài Thơ mountain, Đầu Gỗ cave, and Bãi Cháy.

Five hundred years ago, Nguyễn Trãi described the beauty of Hạ Long Bay in his poem Lộ nhập Vân Đồn, calling it "a rock wonder in the sky." In 1962, the Ministry of Culture, Sports, and Tourism of North Vietnam included Hạ Long Bay in the National Relics and Landscapes publication. In 1994, the core area of the bay was listed as a UNESCO World Heritage Site under Criterion VII and again under Criterion VIII.

Etymology

The name Hạ Long (in Chinese characters: 下龍) means "descending dragon."

Before the 19th century, old books from the country did not mention Hạ Long Bay. Instead, the area was known by other names, such as An Bang, Lục Thủy, and Vân Đồn. In the late 19th century, the name Hạ Long Bay appeared on a map made by France. A French newspaper called Hai Phong News wrote, "Dragon appears on Hạ Long Bay."

According to a local story supported by national pride during the 1800s under the Nguyễn dynasty, Vietnam was fighting invaders to protect its land. To help the Vietnamese, gods sent a family of dragons as protectors. These dragons began to spit out jewels and jade. The jewels turned into the islands and small islands scattered across the bay, connecting to form a strong barrier against the invaders. Magic caused many rock mountains to suddenly rise from the sea, blocking the invaders' ships. The ships crashed into the rocks and into each other. After the battle, the dragons enjoyed peaceful views of Earth and chose to live in the bay. The place where the mother dragon landed was named Hạ Long. The area where the dragon’s children gathered around their mother became Bái Tử Long Island (Bái: to serve, Tử: children, Long: dragon). The place where the dragon’s children moved their tails strongly was called Bạch Long Vĩ Island (Bạch: white, from the foam created by their movement, Long: dragon, Vĩ: tail). This location is now the Tra Co peninsula in Móng Cái.

Overview

Hạ Long Bay is made up of about 1,600 large limestone islands covered with thick jungle. These islands rise from the ocean and some have large caves inside. One of the largest caves is called Hang Dau Go, also known as Grotte des Merveilles by French visitors in the late 1800s. This cave has three big rooms filled with many stalactites and stalagmites, as well as old French graffiti. Two larger islands, Tuần Châu and Cát Bà, have people living there and also have hotels and beaches. Many smaller islands have beautiful beaches.

Around 1,600 people live on Hạ Long Bay in four fishing villages: Cua Van, Ba Hang, Cong Tau, and Vong Vieng. These people live on floating homes and earn a living by fishing and raising marine life, such as 200 types of fish and 450 kinds of shellfish. Many islands are named after their shapes, like Voi Islet (elephant), Ga Choi Islet (fighting cock), Khi Islet (monkey), and Mai Nha Islet (roof). About 989 islands have names. Birds and animals such as bantams, antelopes, monkeys, and lizards also live on some islands.

Most islands look like tall towers in a landscape called fenglin, with heights between 50 and 100 meters. Some islands have lakes inside, like Dau Be island, which has six lakes formed in special rock formations.

Hạ Long Bay is in northeastern Vietnam, between specific coordinates. It stretches from Quang Yen town, past Hạ Long city, to Vân Đồn District. The bay has a coastline of 120 kilometers and covers about 1,553 square kilometers. UNESCO has designated part of the area as a World Natural Heritage Site, including 434 square kilometers with 775 islands.

The climate is tropical and wet, with hot and rainy summers and cold, dry winters. Average temperatures range from 15 to 25 degrees Celsius, and yearly rainfall is about 2 to 2.2 meters. Tides in the bay rise and fall by about 3.5 to 4 meters each day. Salt levels in the water range from 31 to 34.5MT in dry seasons and are lower in rainy seasons.

Out of 1,969 islands, only about 40 are inhabited. These islands are mostly in the east and southeast of the bay. In recent years, many people have moved to live on islands like Sa Tô and Thắng Lợi.

About 1,540 people live in Hạ Long Bay, mainly in Cửa Vạn, Ba Hang, and Cặp Dè fishing villages. Most residents live on floating homes and boats. Fish are fed every other day for up to three years before being sold to restaurants for about 300,000 Vietnamese dong per kilogram. Improved tourism has helped residents earn more money by offering boat tours, accommodations, and seafood to visitors.

The Quảng Ninh provincial government is working to move some families from the bay to safer areas to improve their lives and protect the natural heritage. Over 300 families have been relocated to Khe Cá Resettlement Area, now called Zone 8, since 2014. This project will continue, and only a few fishing villages will remain for tourists to visit.

History

Archaeological sites such as Mê Cung and Thiên Long are found in Hạ Long and Bái Tử Long. These areas include remains of shellfish mounds, such as Cyclophorus and Melania (also called Thiana), some freshwater mollusks, and simple tools used for work. The people of Soi Nhụ lived by fishing, collecting shellfish, gathering fruits, and digging for bulbs and roots. Their environment was a coastal area, different from other Vietnamese cultures like those in Hòa Bình and Bắc Sơn.

In Hạ Long and Cát Bà island, the people developed methods to use the sea for survival. The Cái Bèo culture connects the Soi Nhụ culture to the Hạ Long culture.

Hạ Long Bay was the location of important naval battles between Vietnam and its coastal neighbors. Three times, Vietnamese forces stopped Chinese invaders from landing in the maze-like channels of the Bạch Đằng River near islands. In 1288, General Trần Hưng Đạo prevented Mongol ships from moving up the Bạch Đằng River by placing wooden stakes with metal tips during high tide, which sank the fleet of Kublai Khan.

In 1948, the first time the new national flag of the Provisional Central Government of Vietnam was raised was at Hạ Long Bay. This happened on June 5 during the signing of the Halong Bay Agreements (Accords de la baie d’Along) by High Commissioner Emile Bollaert and President Nguyễn Văn Xuân.

During the Vietnam War, the United States Navy placed many mines in the channels between the islands of Hạ Long Bay. Some of these mines remain today and still pose dangers to ships.

Geology and geomorphology

In 2000, UNESCO's World Heritage Committee added Hạ Long Bay to the World Heritage List because it shows important examples of Earth's history and has unique limestone karst landforms. The area is part of a large rock structure called the Sino-Vietnamese composite terrane, which has changed over time from before the Cambrian period to today. During the Phanerozoic era, layers of rock containing fossils like graptolites, bivalves, brachiopods, fish, corals, and plants were separated by 10 gaps in the rock layers. However, the boundary between the Devonian and Carboniferous periods is considered continuous. The limestone karst landforms in the bay began forming in the Miocene period, especially cone-shaped hills (fengcong) and tall, isolated limestone towers (fenglin). These features include old caves, foot caves, and marine notch caves, creating unique landforms. The Quaternary period had five cycles of changes between ocean and land environments. Today’s Hạ Long Bay formed after the Middle Holocene, leaving limestone cliffs with oyster shells that are 2280 to over 40,000 years old. The area has many resources, including anthracite, petroleum, limestone, and minerals like kaolin and silica sand. It also has surface water, groundwater, and thermal mineral water.

Marine geology shows that Hạ Long Bay is a coastal environment where calcium carbonate dissolves quickly in alkaline seawater, forming unusual marine notches. The bottom sediments range from clay to sand, with silty mud and clay being most common. About 60 to 65% of the sediment comes from living organisms. Coral reef sediments are mostly sand and pebbles, with over 90% being carbonate materials. Intertidal zone sediments vary from clay to gravel, depending on environments like mangrove swamps and beaches. On small beaches, sand may be made of quartz or carbonate.

Evidence of geological events during the Quaternary period includes sediment layers in the intertidal zone, ancient riverbeds, cave systems, marine notches, beaches, and mangrove swamps. Hạ Long Bay’s limestone layers, combined with a hot, wet climate and slow tectonic movement, allowed karst features to develop for 20 million years. The bay has many karst landforms, such as karst fields. It is a mature karst landscape shaped by a warm, wet climate over 20 million years. Karst formation has five stages, with the second stage creating do line karst. The third stage forms fengcong karst, seen in hills on Bo Hon and Dau Be Inland. These hills average 100 meters in height, with some reaching over 200 meters. Fenglin karst includes steep, separate towers, like the rocky islands in the bay, which are 50 to 100 meters tall. Flooded karst depressions became lakes, such as the six lakes on Dau Be Island. The bay has fengcong, fenglin, and karst plain features, which result from uneven erosion processes. Marine erosion created notches that sometimes became caves, forming the mature landscape.

The main caves in Hạ Long Bay are from older stages of karst development. Three types of caves exist:

• Old phreatic caves (e.g., Sung Sot, Tam Cung, Lau Dai): These are large, water-formed caves. Sung Sot Cave is on Bo Hon Island, with a passage over 10 meters high and wide. Tam Cung Cave has three chambers formed by limestone layers. Lau Dai Cave has passages over 300 meters long on Con Ngua Island.

• Old karstic foot caves (e.g., Trinh Lu, Bo Nau): These are horizontal caves near the base of limestone hills. Trinh Lu Cave is 80 meters long with a ceiling 12 meters above sea level. Bo Nau Cave cuts across tilted limestone layers.

• Marine notch caves: These form where seawater dissolves limestone and waves erode cliffs, creating notches that may become caves. Some extend into flooded depressions now filled with tidal water.

A key feature of marine notch caves is their smooth, horizontal ceilings. Some caves formed at levels above or below current sea level.

Ecology

Ha Long Bay has two ecosystems: a tropical, moist, evergreen rainforest and a marine and coastal ecosystem. Seven endemic species live in the bay, including Livistona halongensis, Impatiens halongensis, Chirita halongensis, Chirita hiepii, Chirita modesta, Paraboea halongensis, and Alpinia calcicola. Bioluminescent plankton also live in the area.

The many islands in the bay are home to many other species, such as 477 magnoliales, 12 pteris, 20 salt marsh flora, 4 amphibians, 10 reptiles, 40 birds, and 4 mammals.

Common aquatic species in the bay include cuttlefish (mực), oyster (hào), cyclinae (ngán), prawns (penaeidea (tôm he), panulirus (tôm hùm), parapenaeopsis (tôm sắt)), sipunculoideas (sá sùng), nerita (ốc đĩa), charonia tritonis (ốc tù và), and cà sáy. A new sponge species, Cladocroce pansinii, was discovered in underwater caves near the bay in 2023.

Tourism has caused some environmental changes, such as the clearing of mangroves and seagrass beds and the construction of jetties and wharves for tourist boats. Game fishing near coral reefs is harming many endangered fish species.

Local governments and businesses recognize these problems. They have taken steps to reduce the impact of tourism, such as offering eco-friendly tours and enforcing strict waste management at resorts. These efforts aim to protect the environment while supporting sustainable economic growth.

Awards and designations

In 1962, the Vietnam Ministry of Culture, Sport and Tourism named Hạ Long Bay a 'Renowned National Landscape Monument'.

Hạ Long Bay was first added to the UNESCO World Heritage List in 1994 because of its exceptional beauty that is valued worldwide. In 2000, the World Heritage Committee also recognized the bay for its unique geological and landform features, and its World Heritage status was updated.

In October 2011, the World Monuments Fund added the bay to the 2012 World Monuments Watch, noting that tourism and related developments posed risks to the site that needed to be addressed.

In 2012, the New 7 Wonders Foundation officially named Hạ Long Bay as one of the New 7 Wonders of Nature.

Hạ Long Bay is also a member of the Club of the Most Beautiful Bays of the World.

Popular culture

In writings about Hạ Long Bay, the following Vietnamese writers described the bay in these ways:

• Nguyễn Trãi: "This wonder is ground rising up into the middle of the high sky."
• Xuân Diệu: "Here is the unfinished creations of the Beings…Here are the stones that the Giant played with and threw away."
• Nguyên Ngọc: "…to form this first-rate wonder, nature only uses: Stone and Water…There are just two materials chosen from many, in order to write, draw, sculpt, and create everything…It is quite possible that here is the image of the future world."
• View of the bay by Ho Chi Minh: "It is the wonder that one cannot share with others."
• Phạm Văn Đồng: "Is it one scenery or many sceneries? Is it the scenery in the world or somewhere else?"
• Nguyễn Tuân: "Only mountains accept to be old, but Hạ Long's sea and waves are young forever."
• Huy Cận: "Night breathes, stars wave Hạ Long's water."
• Chế Lan Viên: "Hạ Long, Bái Tử Long – Dragons were hidden, only stones still remain. On moonlight nights, stones meditate as men do…" Lord Trịnh Cương overflowed with emotion: "Mountains are glistened by water shadow, water spills all over the sky."

The people who live in the bay and nearby cities have shared many old stories that explain the names of islands and caves in the bay.

• Đầu Gỗ cave ("the end of wooden bars" cave): These wooden bars in the cave are the remains of sharp wooden columns built underwater by Trần Hưng Đạo, a military leader, to sink Mongolian invaders' ships in the 13th century.
• Kim Quy cave ("Golden Turtle" cave): It is said that the Golden Turtle swam to the Eastern Sea (also called the South China Sea) after returning a holy sword that helped King Lê Thái Tổ defeat Chinese invaders. With the Sea King's approval, the Golden Turtle fought monsters in the area. The turtle became tired and died in a cave, which was then named the Golden Turtle Cave.
• Con Cóc islet (Frog islet): This islet looks like a frog. According to an old story, during a severe drought, a frog led all animals to the heavens and protested to the God. They demanded rain, and the God agreed to make the frog his uncle. Since then, whenever frogs grind their teeth, the God must send rain to the ground.
• Hang Trống and Hang Trinh Nữ (Male cave and Virgin cave): A tale tells of a beautiful woman who fell in love with a fisherman. After they became engaged, the fisherman had to go to sea. A landlord saw the woman, captured her, and exiled her to a remote island. She died of starvation and turned into a statue called Hang Trinh Nữ (Virgin Cave). Her lover arrived at the island, learned what had happened, and turned into an islet nearby called Hang Trống (Male cave).
• Thiên Cung cave (Paradise cave): This cave is linked to the ancient Dragon King. It is said that the Dragon King's seven-day wedding took place here. Many dragons and elephants came to celebrate by dancing and flying.
• Sửng Sốt Cave (Surprise Cave): Local stories connect the large chambers and detailed rock formations in this cave to a mythical palace of the Dragon King or a gathering place for celestial beings. Its name reflects the surprise people feel when entering the cave's large interior.
• Luồn Cave (Tunnel Cave): According to local tales, this low, water-level cave was believed to be a secret path used by dragons and sea spirits to move between sacred parts of the bay. Passing through the cave is sometimes described as crossing a symbolic boundary between different parts of nature.

Conservation issues

Ha Long, Hai Phong, and Hanoi are important cities that help the economy grow in northern Vietnam. The economic growth in these cities, along with the fast development in southern China, including Hong Kong, has increased pressure on Ha Long Bay. The coastal areas of Quang Ninh province and Hai Phong City have seen rapid growth in transportation, shipping, coal mining, and tourism-related industries. Since 1999, the Asian Development Bank (ADB) has warned that building new ports in Ha Long Bay could increase maritime traffic, harming the bay’s infrastructure and the systems that support tourism. Pollution from industrial waste, overuse of natural resources, and overfishing also threaten the bay. Some experts say that development in the bay should be carefully managed because the area is very important for the environment.

Today, the expansion of cities, population growth, port and factory construction, tourism activities, waste from homes and industries, and fishing practices have caused serious environmental pollution and changes to the landscape of Ha Long Bay. Because of pollution, coral reefs in the deep sea of Ha Long Bay are getting worse. The once-clear waters of the bay are becoming more muddy and filled with sediment, leading scientists to warn that the bay might become "flooded." Additionally, the thousands of limestone islands that surround Ha Long Bay are often used as building materials, making them vulnerable to private mining, which harms the natural landscape.

Another challenge is global climate change, which causes rising sea levels. This change threatens the islands, caves, and wildlife in Ha Long Bay. Vietnam does not have enough people or supplies to fully address these problems.

In terms of culture, many international tourists have complained about the lack of environmental awareness among visitors and local people. The goal of making Ha Long Bay a modern, respectful, and welcoming place for tourists has not been fully achieved. Some people still bother tourists by asking for money, which harms the tourism experience at the heritage site. Raising awareness through education, limiting resort development on islands, and enforcing eco-tourism rules and conservation laws are important challenges for the local government. Some caves in Ha Long Bay have been damaged, with stalactites broken or taken for decoration (2016). Some caves have even been covered with concrete to be used as banquet halls. Fishing boats and tourists also leave large amounts of waste, which local authorities have not managed well.

To reduce the harm caused by human activities, the government of Quang Ninh province has banned fast motorboats that carry tourists in the bay to protect the environment and wildlife. The province has also moved fishing families living on floating villages to the mainland to protect the water quality of Ha Long Bay. Mining coal and stone within the heritage area has been stopped to prevent pollution, as advised by UNESCO. Some local residents have formed volunteer groups to collect and handle waste to help preserve the landscape. Starting September 1, 2019, the People’s Committee of Ha Long City banned the use of single-use plastic products in the bay area. This is an important step to protect the environment.

The similar landscapes, geology, wildlife, and cultural and historical value of Ha Long Bay, Cat Ba Archipelago, and Bai Tu Long Bay have led to research and activities in geology, archaeology, culture, and tourism that extend beyond Ha Long Bay. Some experts suggest expanding the conservation area to include not only Ha Long Bay but also nearby sea areas near the Vietnam–China border. This region, which is about 300 km long and 60 km wide, can be protected as a unique marine ecosystem in Vietnam.