Picking up a beach towel on your way out the door might not be a decision you mull over—maybe you just grab whatever is available, even if that’s the same faded number you’ve been using forever. While ...

a towel, a robe and a key for your locker—and a chance to sign up for a 25-, 50-, or 75-minute massage ($100-$250). Then, you are set free to roam the spa, which is full of relaxation rooms ...