Every fact below names its source and the month we checked it. Local legends are labelled as legends. Spotted a mistake? Tell us through the contact page.
On 16 September 2023 UNESCO extended the listing to include the Cat Ba archipelago, so the site is now called Ha Long Bay - Cat Ba Archipelago.
The extension was approved at the 45th session of the World Heritage Committee, after a revised nomination went to UNESCO in early 2021. The site now spans both Quang Ninh province and Hai Phong city, because Cat Ba Island is administered by Hai Phong. The board describes it as covering seven adjacent ecosystems and the habitat of many rare animal species.
Source: Ha Long Bay Management Board. Checked October 2026.
Ha Long Bay covers 1,553 square km and holds 1,969 islands of many sizes.
The 1,553 square km figure covers the whole bay, and the islets are mostly made of limestone. The count of named islands differs between sources, so there is no single fixed number. Many names come from shapes: Voi Islet means elephant, Ga Choi means fighting cock, Khi means monkey and Mai Nha means roof.
Source: Ha Long Bay Management Board, Wikipedia, Ha Long Bay. Checked October 2026.
The part of the bay inside the UNESCO listing is 434 square km, with 775 islands, 411 of which have names.
The UNESCO site is one part of the wider bay, bordered by three points: Dao Dau Go in the west, Dao Dau Be in the south and Dao Cong Tay in the east. The bay was recognised in 1994 for its aesthetic value and again in 2000 for its geology and geomorphology.
Source: Ha Long Bay Management Board. Checked October 2026.
More than 2,900 species of plants and animals live on land and in the sea around the bay, across 10 different ecosystems.
The management board counts nearly 3,000 species of plants and animals, spread across 10 ecosystems from marine to forested areas. They include island vegetation, caves, mangroves and regularly flooded coastal wetlands. The board's own pages give slightly different totals, more than 2,900 in one place and nearly 3,000 in another, so read the figure as a round one.
Source: Ha Long Bay Management Board. Checked October 2026.
The karst towers of the bay took about 20 million years to form under a tropical wet climate.
A landscape like this needs a massive thickness of limestone, a hot wet climate and slow tectonic uplift. The process has five stages, and the bay shows several of them. One is fengcong karst, groups of hills shaped like cones with sloping sides, which average 100 m in height.
Source: Wikipedia, Ha Long Bay. Checked October 2026.
Four caves named by the bay's management board are Thien Cung, Dau Go, Sung Sot and Trinh Nu.
The board describes the cave systems hidden inside the islands as a major part of the bay's beauty, and many are tied to folklore, Trinh Nu Cave among them. Thien Cung, Dau Go and Sung Sot are named alongside countless others. A geologist, Tony Waltham, studied 32 caves among other sites during a 1998 visit.
Source: Ha Long Bay Management Board. Checked October 2026.
Around 1,600 people live on the bay itself, in four fishing villages.
The four villages are Cua Van, Ba Hang, Cong Tau and Vong Vieng, in Hung Thang ward of Ha Long city. People live in floating houses and earn a living from fishing and marine aquaculture. Wikipedia notes that residents now also rent out bedrooms, run boat tours and serve seafood meals to tourists.
Source: Wikipedia, Ha Long Bay. Checked October 2026.
The poet Ho Xuan Huong visited the bay between 1814 and 1818 and wrote five poems in Chinese about it.
Ho Xuan Huong travelled widely during her visit to Yen Quang, now Quang Yen town. The research work Ho Xuan Huong and Ha Long Bay by Professor Hoang Xuan Han records her five poems about the bay. In one of them, Trao Ca Thanh, she paints the landscape as a watercolour, with sparkling waters all around under a veil of clouds.
Source: Ha Long Bay Management Board. Checked October 2026.
Local legend, not a verified fact
Local legend says dragons sent by the gods spat jewels that became the bay's islands. The mother dragon came down at Ha Long, which means descending dragon.
In the legend, the gods sent a family of dragons to help the Vietnamese defend their land. The jewels and jade the dragons spat became islands that linked into a wall, and invaders' ships struck the rocks. Wikipedia says this version was reinforced by nationalism in the 1800s, so read it as a story, not as history.
Source: Wikipedia, Ha Long Bay. Checked October 2026.
Climate, airports and UNESCO status for Ha Long Bay are on its destination page. More places are on the fun facts index.