This UNESCO World Heritage area, also known as Halong Bay on land, stretches along the Ngo Dong River and is flanked by views of majestic karst cliffs, limestone caves, grottoes, and vibrant green rice fields. Tam Cốc literally translates to “three caves,” referring to the Ca, Hai and Ba caves carved by centuries of flowing water. Locals often refer to the surrounding fields as the Green Sea, a poetic nod to the way the wind ripples through the endless rice paddies like waves