Crazy isn't it? Sand Dunes floored me. I wasn't expecting it at all. We were driving toward it and we saw some sand thinking "oh, there it is." But that wasn't it, and we kept driving toward something larger, and eventually we started going down and we realized these mountainous things were the dunes. Snow-capped peaks with dense vegetation on the side and 800 foot sand dunes at the base with a snow-melt stream running in along the side. Truly unique. One of my top 5 parks (out of 25, whew!).
none. I saw one in Big Bend though!