Ha Long Bay is located in the northeastern part of Vietnam and constitutes part of the western bank of Bac Bo Gulf, including the sea area of Ha Long City and Cam Pha Town and part of Vân Don island district. It abuts Cat Ba Island in the southwest. Toward the west is the shore with a 120 km-long coastline. It is located within 106o58’-107o22’ east longitude and within 20o45’- 20o50’ north latitude. The site is 1553 sq. km with 1969 islands of various sizes, of which 989 have been named.

 

The islands in Ha Long Bay are mainly limestone and schist islands most lying in the two main areas: the southeastern part of Bái Tử Long Bay and southwestern part of Hạ Long Bay. These islands represent the most ancient images of a geographical site having a tectonic age of from 250 million to 280 million years.