Hạ Long Bay is a UNESCO World Heritage Site and popular travel destination in Quảng Ninh Province, Vietnam. The bay features thousands of limestone karsts and isles in various shapes and sizes. Hạ Long Bay is a center of a larger zone which includes Bái Tử Long Bay to the northeast, and Cát Bà Island to the southwest. The limestone in this bay has gone through 500 million years of formation in different conditions and environments. The evolution of the karst in this bay has taken 20 million years under the impact of the tropical wet climate.
Thanks to Dr Kiran Acharya.