O Quy Ho Pass is one of the most impressive mountain routes in northern Vietnam, crossing the Hoang Lien Son range along National Highway 4D. The pass stretches for nearly 50 km between Sa Pa and Tam Duong, with its highest point reaching approximately 2,035 metres above sea level, making it the highest of Vietnam’s famous “Four Great Passes.” 

The journey is characterised by steep mountain slopes, winding bends, deep valleys and dramatic changes in weather. On clear days, the route provides expansive views across the Hoang Lien Son mountains, while clouds and mist frequently create an atmospheric highland landscape. From viewpoints around the pass, visitors may also see Fansipan, Vietnam’s highest peak, rising above the surrounding mountains. 

One of the most popular stops is O Quy Ho Sky Gate, located at the highest section of the pass. At around 12–18 km from central Sa Pa, the viewpoint is particularly popular for cloud hunting, panoramic photography and sunset or sunrise views. 

O Quy Ho Pass is especially attractive from September to April, when cooler weather and frequent clouds create a distinctive highland atmosphere. However, conditions can change quickly at this altitude, particularly in winter, when temperatures can become very low and fog or ice may occur. The pass is commonly combined with Silver Waterfall, Love Waterfall and Fansipan as part of a scenic day trip from Sa Pa.