Given you'll probably spend a decent amount of your time at the hotel in a fluffy robe and slippers, you won't need to bring too many belongings. Besides comfortable clothes to wear after your spa treatments, essential items like underwear and deodorant should be right at the top of your packing list. Of course, if you intend to make use of the pool or steam room, or get physical with an exercise class or two, toss a swimming suit and some gym attire in your bag as well. Finally, leave the smartphone and laptop behind and take a good read instead. It is, after all, meant to be an escape from the real world.