Nearly 3,000 limestone islands, called karsts, emerge mystically from the waters of the Gulf of Tonkin. Ha Long Bay, translated literally as the Bay of Descending Dragons, was declared a World Heritage Site by UNESCO in 1994. A Ha Long Bay cruise to take in these strangely sculpted karsts, which hide caves, lagoons and beaches, is a must on any Vietnam vacation. Add a kayaking excursion for an up-close-and-personal experience of this dream-like masterpiece of nature as you explore hidden caves that are only revealed at low tide through the chinks in the cliffs.