Wow there!
This looks very nice. What I especially like is the gradient applied to the trees, I really think that looks cool.
I would like to point out that the stone blends in with other stone even when they are of different depths. For example, down below, the pillars do not stand out enough so that they can be distinguished from the stone behind it.
I suggest adding a new set of colors near that area, setting the sun pretty low down so shadows are sideways and elongated, or simply adding other lighting effects.
I do not even know if this critic is useful to you because it focuses more on lighting than building, but hope that helps!