The outer gas disk of our Galaxy (and many others) is warped, bending away from the plane defined by the inner disk. The bend begins just outside the solar circle; gas at longitudes ℓ ≃ 80° reaches highest above the plane, while material at ℓ ≃ 260° lies below it. Shortwavelength ripples are superposed. The orbit of a free particle inclined to the galactic disk precesses at a rate which depends on galactocentric radius; warped structures will tend to do the same, winding the warp into a tight spiral. The large-scale galactic warp has no sense of spirality, and is not obviously of recent origin - why then has it survived?