Tham Phu Kham & Blue Lagoon Vang Vieng

Located west of Vang Vieng, the vast Tham Phu Kham is considered sacred by Lao. The main cave chamber contains a Thai bronze ­reclining Buddha, and from here deeper galleries branch off into the mountain. It's hugely popular largely due to the lagoon in the cave, but overdevelopment, group tourists and noisy buggies have made it an unpleasant place to swim.