Halong Bay is located in Quáng Ninh province, Vietnam. The bay features thousands of limestone karsts and isles in various sizes and shapes. The bay has a 120 kilometre long coastline and is approximately 1,553 square kilometres in size with 1969 islets. Several of the islands are hollow, with enormous caves, other support floating villages of fishermen, who ply the shallow waters for 200 species of fish and 450 different kinds of mollusks. Another specific feature of Halong Bay is the abundance of lakes inside the limestone islands, for example, Dau Be island has six enclosed lakes. All these island lakes occupy drowned dolines within fengcong karst.