Hai Van Pass, or 'Ocean Cloud Pass', is a journey truly destined to be experienced by rail. This 21 km stretch of the Annamite Range creates a dramatic, mist-shrouded limestone barrier between the modern skyline of Danang and the imperial soul of Hue in Central Vietnam. Historically, these peaks served as a formidable geopolitical wall, separating the ancient kingdoms of Champa and Dai Viet for over 160 years. Today, while the highway winds across the summit, it is the North-South Railway that offers the most intimate, untouched encounter with this legendary landscape.