Our day at Great Sand Dunes NP was heavily overcast; a great day for a portrait shoot, but not to shoot these dunes.  But on our departure the next day, enough sun broke through to give the dunes some shape in my photos.  The one I chose for February is my favorite.

These dunes are massive, rising 650 feet above the valley floor.  Now the photo below is not a good photo, per se, but its purpose is to show the scale.

The people in the photo do that (scale).  I thought I would try to walk to the top.  I got maybe half way (that peak just right of the middle of the photo).  The altitude (8200 feet at the base), elevation gain, and the difficulty of walking on the sand proved more than I was able to conquer.  I made it halfway.  Better to live and photograph another day, I thought.

The other value of providing this photo is to illustrate what I said about about the need for low angle, directional light to give depth and contour to the dunes.