Viet Nam travel: Hai Van Pass The Hai Van Pass (also Ai Van Pass or ocean cloud pass) is 500 above sea levels with length of 21km. This pass is on the border of Thua Thien Hue (at the North) and Da Nang (at the South) , near Bach Ma National Park. It is the most dangerous and longest in Vietnam. Viet Nam travel: Hai Van Pass The Hai Van Pass (also Ai Van Pass or ocean cloud pass) is 500 above sea levels with length of 21km. This pass is on the border of Thua ... Read more » 7:28 PM