Hạ Long Bay is a UNESCO World Heritage Site located in northeastern Vietnam. It is famous for its emerald waters and thousands of limestone islands topped with rainforests. The bay covers an area of approximately 1,553 square kilometers and features around 1,600 islands and islets, many of which are uninhabited. Visitors to Hạ Long Bay can enjoy activities such as boat tours, kayaking, and exploring caves. The bay is also home to diverse marine life and unique ecosystems, making it a popular destination for nature lovers and adventure seekers alike.