Quick Field Data
- UNESCO Inscription: 1994, extended in 2000 and enlarged with the Cat Ba Archipelago in 2023 · Criteria (vii), (viii)
- Scale & Footprint: 65,650 hectares with 1,133 islands and islets in Quang Ninh Province and Hai Phong City, northern Viet Nam
- Access & Ticketing: The bay is seen from licensed tour boats, on day trips or overnight cruises that stop at caves and islands
- Arrival Logistics: Ha Long City is about 170 kilometres east of Hanoi, around two and a half to three and a half hours by road; Tuan Chau port is the main departure point for overnight cruises
How the Sea Drowned a Limestone Landscape
Ha Long Bay is a landscape of limestone. The rock formed over hundreds of millions of years, and the karst landforms developed over about 20 million years in a hot, wet climate. Rain dissolved the limestone into cones and towers. Later the sea rose and flooded the low ground between them.
UNESCO calls the result the most extensive and best-known example of marine-invaded tower karst in the world. Geologists name two forms here. Fengcong is a cluster of cone-shaped peaks. Fenglin is a field of separate towers. Ha Long shows both, and UNESCO says it records every stage of the sea flooding a tropical karst.
Most towers are 50 to 100 metres high. Waves have cut notches at their base, and many islands have sheer cliffs that drop straight into the water. Inside some islands are enclosed lakes in drowned sinkholes. Some of these lakes appear to rise and fall with the tide. The tidal range in the bay is around 3.5 to 4 metres.
The protected area covers two connected parts. Ha Long Bay lies to the north-east in Quang Ninh Province. The Cat Ba Archipelago lies to the south-west and belongs to Hai Phong. Cat Ba Island is the largest island in the region, at about 262 square kilometres, with a steep, forested interior.
Caves, Legends and the Cat Ba Archipelago
The name Ha Long means descending dragon. A local legend tells of dragons sent to protect the country. The jewels and jade they spat out became the islands. The place where the mother dragon came down was named Ha Long.
The caves are the most visited part of the bay. UNESCO groups them into three types: remnants of old water-filled caves, foot caves at the base of towers, and notch caves cut by the sea. Dau Go is the largest grotto in the Ha Long area, with three large chambers. The French called it the Grotte des Merveilles. Sung Sot and Thien Cung are other well-known caves.
The bay also has a long human history. In 1288 the Vietnamese general Tran Hung Dao defeated a Mongol fleet in the nearby Bach Dang River by planting wooden stakes in the riverbed. For generations, fishing families lived in floating villages such as Cua Van and Vong Vieng. Since May 2014, more than 300 households have been moved to new homes on shore.
Cat Ba adds a different side. Cat Ba National Park was created in 1986 and covers a large part of the island. The archipelago became a UNESCO biosphere reserve in 2004 and joined the World Heritage site in 2023. Its best-known animal is the Cat Ba langur, a critically endangered monkey found only here. There were once 2,400 to 2,700 of them, but numbers fell to as few as 53 in 2000. About 68 now live in the wild.
The islands support other rare life as well. UNESCO lists an endemic palm, Livistona halongensis, and the Cat Ba tiger gecko. Threatened species here include the keeled box turtle, the Asian small-clawed otter, the mainland serow and the king cobra.
Ha Long Bay was first protected as a national scenic site in 1962 and became a special national monument in 2009. Tourism, shipping and fishing are heavy in the bay. UNESCO notes that the scenery and key landforms remain intact, but that keeping the water clean and visitor numbers in check are ongoing challenges.
Cruising the Bay and Visiting Cat Ba Today
Nearly all visits are by boat. Day trips run a few hours, while overnight cruises go further among the islands and stop at caves, beaches and kayaking spots. The climate has a hot, wet summer and a cooler, drier winter.
- Choose Your Port and Route: Most overnight cruises leave from Tuan Chau port, close to Ha Long City. Day boats also use the Ha Long International Cruise Port in the city. Check which caves and islands your route includes before booking, because routes differ between operators.
- See a Cave and Explore Cat Ba: Cave visits involve steps and uneven paths, so wear good shoes. On Cat Ba Island, the old town of Cat Ba is a base for Lan Ha Bay. Inland you can visit the Hospital Cave, used as a bomb-proof hospital until 1975, and Cannon Fort on a 177-metre peak above the bay.
- Watch the Weather and Plan Onward Travel: Storms can arrive fast in the wet season. In July 2025 a tourist boat capsized in a sudden thunderstorm on the bay, and dozens of people died. Follow crew instructions, wear a life jacket on small boats and accept cancellations when warnings are issued. See other natural sites in our UNESCO World Heritage Atlas, and return to Hanoi, our closest city guide.
