Given you'll probably spend a fair amount of your time in a robe and slippers, you won't need to bring a lot. Besides comfy, loose-fitting clothes to change into after your pampering treatments, personal items such as underwear and toiletries should be at the top of your packing list. Of course, if you intend to make use of the hot tub or pool, or engage in exercise sessions, throw a bathing suit and some gym attire in your bag too. Finally, leave the electronic devices behind and take something light to read instead. It is, after all, meant to be an escape from the real world.