Champasak (or Champassak) is a province in the far southwest of the country, through which the river Mekong flows, and which borders both Thailand and Cambodia. Its capital is Pakse and the region is important in both Lao and Siamese history.
Sights in this peaceful and rural province include the Khmer ruins of Wat Phou, which has structures dating from the 11th-century, and whose shrine is a centre for Theravada Buddhism. It's older than the Angkor temples, but magically tranquil by comparison - still half dilapidated and shrouded in jungle mist.
The picturesque Khone Falls and Pha Pheng Falls on the Mekong River plunge 21 metres, and contain a small population of endangered Irrawaddy Dolphins downstream. The broader reaches downstream are known Si Phan Don or Sipandon (4000 islands) - huge riverscapes with paddy fields, stilted houses and tiny sandbank islands, a few of which are starting to become popular with adventurous travellers (only a handful have electricity, for example).
But mostly visitors to the region come to sample its unspoiled rural way of life around the Mekong, and for the chance to visit minority villages and learn about their customs and practices - silk weaving, fishing (including the giant catfish, the world's largest freshwater fish), buffalo breeding (and sacrificing), and local markets (including some delicacies you might prefer not to taste!).