With those nice clouds I'd try and adjust the sky a little darker to give them even more definition. I don't think you need quite so much foreground -- cropping to 640x427 would eliminate some grass and lower the horizon below the midpoint. Also looks pretty good in grayscale.
I find this a pleasant photo, but I get visually confused as to what the subject is here. The clouds, the stone formation, or the tree. I enjoy a photo with visual motion, that is, one that causes the eye to wander from element to element. However, I think this one would benifit more from a different perspective that brings the eye to the subject.
Nice depth of field, color and use of subject matter (trees and rock) to offset what could have been 'just another landscape'. I am not sure what I should focus on as the subject (trees or rock). I find my eyes bouncing back and forth. My natural tendency is to move from left to right so I might have cropped out the trees on the left (though you could do the opposite and remove the rock). I might also have cropped out about half the grass to give more drama to the sky.
A really nice landscape. The clouds are simply breathtaking. I also like the way that the ruins hint at human existance, but the landscape still looks so pristine. EXCELLENT.
Aside from the title, it's difficult to tell where to focus. The tree competes. A bare landscape as a setting for the ruin would be more dramatic. Just by moving you could have changed your perspective. Great coloring. Wonderful clouds.