We also learned that Si Phan Don is much farther than we thought and we wouldn't get there in the time that we had. Phu is the thing to do in Champasak. It has an especially ancient, mysterious, sacred aura, complete with crumbling Hindu ruins, Buddha statuary, and a crocodile carved from rock that was presumably used for human sacrifices. The wat is set into the mountainside, and we climbed very steep and narrow treacherous steps to reach it. Traveling in the North is much easier than it is in the South.
Buses depart all day long from two of Vientiane's main markets.
For those with plenty of time, Vang Vieng is just the first stop on the way to Luang Probang. In contrast to traveling in the south, where we were often the only tourists, half of the passengers on the bus to Vang Vieng were Anglo. It is an easy four-hour ride, and once there you will find plenty of clean and cheap guest houses. I stayed at a lovely French colonial, the Dokkhoun Guest house. The hillside caves are Vang Vieng's main attraction.