I did the Thakhek motorbike loop with two German girls. It is amazing to do. We did it in thee days and saw some incredible stuff. From views to waterfalls and from caves to villages. When you have the time do the motorbike loop in Thakhek.
In our motorbike loop from Thakhek we visited on the 3th morning the Konglor Cave. It is a special cave to visit. You walk into the cave and there you go on a small wooden boat with small engine. Two guides will take care of you and the boat during the boat ride.