I got good stuff from just past the start of the primitive road to the Point of No Return sign. I kept stopping at every pullout I came to and walked around a bit. I would say it's about a mile or so. But it may seem longer walking in the loose sand. If you haven't found it already here is a link to a map of Great Sand Dunes http://www.nps.gov/grsa/planyourvisit/maps.htm