did you try taking this shot with the circle smack dab in the middle of the frame? I'd try to darken the exposre as well, overcast skies are a pain to work with.
nice shot! I like the shadows and the light on the rock wall. The building in the back is not in focus, plus not quite centered. Nice concept of the theme!
Interesting stonework ... might try playing a bit with the reflections in the polished portion too ... because of the darkness of the stonework, your sky was a bit overexposed.
Nice curve, would have been better if you took it at a different time of day ( early morning or evening ) could have gotten some color to the sky insted of bleached out.
I like your choice of subjects for the curves challenge. The amount of light in your photo is very high and maybe a polarizer or a neutral density filter of some sort would have helped some. The top of the building in the background is washed out wiht light and the definition is not quite where I would like to see it... Your 'eye' for the challenge is very good :)
Ouch! This shot is very washed-out. I can't even make out the roof of the building, or the reflections in the rock. Try turning down the white balance on your auto mode.