Ha Long Bay is a UNESCO World Heritage Site of almost otherworldly beauty — some 1,969 limestone islands and islets, most uninhabited, rising sheer from the Gulf of Tonkin. A overnight junk boat cruise is the classic way to experience it, weaving between karst cathedrals, hidden caves, and floating fishing villages. Kayak into secluded lagoons, watch the sunset paint the pillars gold, and wake to mist drifting between the peaks. Nearby Lan Ha Bay and Bai Tu Long Bay offer the same drama with far fewer crowds.