Once out of Lang Co, the Mandarin road starts climbing up the Truong Son mountain range, for tourists, that is, because a tunnel now makes for a less arduous route to the other side of the mountain. At 496m you reach Hai Van Pass ("Cloud Pass"), which marks the border between North and South. As its name would suggest, it is often shrouded in cloud but on a clear day you can enjoy views of the coast bathed by the turquoise waters of the South China Sea and its miles of pristine beaches.