I second that the via ferrata is a fantastic activity. Wasn't as difficult physically as I expected but fantastic views and a general thrilling experience.

I also highly recommend the hike/personal training + massage package the spa offers. A trainer will take you on a 20-30 mins hike to a beautiful wooden platform with a nice hot tub and big open deck, then you have a one hour personal training session followed by a great outdoor thai massage. You can then order some food / drinks and enjoy the hot tub before either walking back (on flat road) or being picked up.