Ha Long Bay

Ha Long Bay, in the Gulf of Tonkin off north-eastern Vietnam, gathers thousands of limestone islands and islets with sheer walls. Its origin lies in a tropical karst developed over millions of years on a limestone platform: the dissolution of the carbonate gradually isolated towers and residual massifs, and the rise in sea level after the last glaciation flooded the valleys between them, leaving only the summits above water. It is therefore a partly submerged tower karst, one of the most extensive and best preserved examples in the world. The islands hold extensive cave systems, inland lakes connected to the sea by submerged tunnels and cliff-dwelling plant communities with local endemics. On some islands the Cat Ba langur survives, one of the most threatened primates on the planet. Tourist pressure and shipping traffic are the main conservation threats. It was inscribed on the World Heritage List in 1994 for its scenic and geological values.