Speleotherapy is a type of therapy where you go into really cool, dark caves filled with salt. The salt comes from all the minerals that are in the rocks, and when they evaporate, it makes the air really, really clean.
When you breathe in the air in the cave, it helps clear out your lungs and helps you breathe better if you have trouble breathing because your lungs are sick. This is a lot like how you cough up mucus when you're sick, but instead, the salt helps get all the yucky stuff out of your lungs.
Many people go speleotherapy because it helps them feel better and can make their lung sickness better. Plus, being in a cool, dark, salt-filled cave can be a fun adventure too!