Very nice - I like that you didn't use the standard "dead on to the arch" perspective. Nice diagonal line created in the first shot, from upper left to lower right.
You might want to try masking and playing with the sky a bit. I can believe that the sun is coming in at such an angle as to hit the rocks but leave the sky and clouds dark, but it still doesn't look quite right. I'm not sure how to make the sky look more like it fits (brighten it? make it more contrasty/stormy?), but take a look at it if you're in the mood to play.