It’s no-frills, but it’s nonetheless striking. This orb-shaped cedar-and-glass cabin in Eugene, at the back of the hosts’ main house—where the cabin's usually private bath is located 30 yards away—is furnished with a fold-down desk and velvet curtains and spruced up by artwork and a white lounge chair. The architecture and simplicity appeal, but so do the surroundings, including the pond, fire pit, and stone pathway. A retro slide and curbside lending library add to the old-timey ambience.