Phong Nha Park near Dong Hoi, Vietnam

It straddles the mountains between the China Sea and the Laos border. It has the biggest caves in the world, and the massive limestone hills are covered with vegetation so that it looks like the set for a King Kong movie.

 

The road south to Khe Sanh was suitable only for walking until lately when they paved it. It was nicknamed the Ho Chi Minh Trail West and is now considered one of the best motorcycle rides in Vietnam.