Excellent sense of scale. The sphere behind the hill subtly dominates the scene by it's size, placement, and faded colours. I also notice how you've set the sphere in the scene by having the clouds at times dispersed by it. That really helps to cement it as natural feature of the landscape rather than somehthing added in hindsight.

The hills have excellent lighting. Very natural and well coloured. Lastly I do like their construction from a compositional point of view. It breaks up the other forms, which are very uniform, quite nicely.