Vang Vieng is situated in the middle of what is technically called a "karst topography." It's strange coming south on Route 13 to Vang Vieng - the hills mutate as you go. You're driving through very hilly terrain on a road that thrashes about like a snake with its head in a trap admiring the beautiful views. The hills become more and more ... lumpy. Like someone with a really big fist got under the crust of the earth and just started punching upwards. They just look wrong, but in a very attractive way.