Halong bay is a very scenic area in the Gulf of Tonkin, 170 km east of Hanoi. The bay consists of a dense cluster of almost 2000 limestone islands and rock formations protruding spectacularly from the sea, each covered with thick vegetation. The area is similar to the Phang Nga bay in southwest Thailand.
Many of the islands are hollow and contain enormous caves. Two of the larger islands, Tuan Chau and Cat Ba, have permanent human settlements. In the Halong bay there are also floating villages of fishermen. Halong bay has been a UNESCO World Heritage site since 1994.