The hills are definitely the most striking part of the photo. They are perfectly exposed and saturated. The menacing clouds compliment them well with their darkness. The road snaking away into the distance gives a good feeling of depth and perspective. The color balance is precisely where it should be as well.
I would have to say that a square crop works particularly well here, and this shot encourages me to try it as well some time.
My only gripe with this shot would be that the dark parts of the image seem ever so slightly underexposed (1/2 stop) and perhaps could use a touch more saturation.
An extremely impressive portrayal of a very special place