Hot Springs ruin

If you want to draw attention to the arch I would sugest cropping the left side quite a bit to cener the arch in the picture. The foilage and black object on the left border are distracting, IMO.

I think if you crop just above the arch a bit and add some magenta. Kind of make a pano out of it. maybe crop just abit of the bottom.

I'm not usually a fan of color, but this photograph works for me. Rather than making the arch the focal point of the photograph, I see it as only one element of a larger composition. The dark crate on the bottom left and the dark stain on the wall on the top right balance each other well. If you crop the left side, you lose the yellow from the tree and therefore, some color balance that you currently have. (Cover it with your hand and you have a very different photograph - not just compositionally, but also the overall color shifts to something less appealing). I think your first instinct was better here - I'd leave it as it is. A photograph about an arch is much less interesting to me than the relationships you have going on here.