The Kuang Si Cascades near Luang Prabang in Laos are, without a doubt, the most beautiful waterfalls I have ever seen. The cascades are a series of waterfalls which not only look impressive but have formed swimming holes where you can splash around enjoy yourself for a few hours.
If you manage to drag yourself away from the swimming holes there are also walks in the area. We however never managed to find the time for this but they come highly recommended from various people we have spoken to who had dragged themselves away from the pool to have a look.
Near the entrance there are also a few enclosures for rescued bears which was an added bonus to see. We arrived around their lunch time so they were very active.