Tell Me About Your Most Rigorous Walk

Last week two Walk It Off guests and I hiked a good hunk of Fire Island, covering well over twenty miles over the course of two days. While I was sweating in the rain, walking on beaches and carrying a fair amount of loose sand in my shoes, it got me thinking about difficult but rewarding walks. So I want to hear from you, what challenging walks have you been on? And how did you feel when you finished?