The strong line of the lighthouse works very well with the negative space of the blue sky. The position of the lighthouse in the frame makes the image very dynamic. The diagonal line of the hill also works and is in stark contrast to the strict geometry of the lighthouse.
The sky is so eerily smooth and hasthe same overall tonality ;) I think the wee little bush on the right makes this shot and compliments the stark white lighthouse.
What a wonderful shot. This is the one I like most. The sky is so blue. And the composition is very dynamic: the hill going down, the building not centered, the negative space in the left...
Very nice.
The only thing I can say to improve the photo is a little bit more of sharpness (maybe using the Unsharp Mask of PS).