Tourists are attract to rent a bike and have a tour with it around the area.
Go and visit the beautiful waterfall known as Kaeng Nyui Waterfall.
Do not forget to visit one of the most famous tourist attraction, the Pha Tang Bridge & temple.
You can cover these both within a day as they are not far and enjoy your day.
Blue Lagoon 3 is about a half an hour drive from Blue Lagoon 1.
Another tourist attraction, this is one of my favorite thing to do in Vang Vieng.
You will feel very satisfy with the adventure of Kayaking on the river.
You can say that this is the most famous thing that travelers do to explore the Tham Chang cave.
Usually, it is only accessible for guests, but if you buy some food or drinks at the restaurant, it should be okay.