The bay has a 120 kilometre long coastline and is approximately 1,553 square kilometres in size with 1969 islets. The area designated by UNESCO as the World Natural Heritage Site includes 434 km² with 775 islets, of which the core zone is delimited by 69 points: Đầu Gỗ island on the west, Ba Hầm lake on the south and Cống Tây island on the east. The protected area is from the Cái Dăm petrol store to Quang Hanh commune, Cẩm Phả town and the surrounding giants zone.

Boats in Halong Bay in the northeast of Vietnam, there are thousands of islands, most of them not much more than big rocks, scattered all over Halong Bay. The tour I did here was certainly a highlight of my visit to Vietnam. It is great to settle on the deck of a boat, and spot limestone rocks rising up vertically from the quiet emerald-green sea, their green-yellow colours reflected in the water, with the shadows of other rocks in the background.

Halong bay is in northeastern Vietnam, from E106°56' to E107°37' and from N20°43' to N21°09'. The bay stretches from Yên Hưng district, past Hạ Long city, Cẩm Phả town to Vân Đồn district, bordered on the south and southeast by the Gulf of Tonkin, on the north by China and on the west and southwest by Cát Bà island.