Phong Nha-Kẻ Bàng National Park
Perhaps the most naturally stunning and well-preserved area in all of Vietnam, Phong Nha-Kẻ Bàng is home to some of the largest caves in the world. The park, which shares a border with Hin Namno Nature Reserve in Laos, covers an area of nearly 900sqkm (347sqmi) and is often a stop for those following the Ho Chi Minh Highway. Gibbons and macaques roam the forests, yet it’s the sprawling karst cave systems that have earned Phong Nha a spot on the Unesco World Heritage list. Hundreds of miles of underground labyrinths run beneath limestone giants as they tower towards the sky.