I love the overall feel of the shot. The right feels a little 'cramped' to me ... perhaps because that is the direction the girls are looking and there is little there in the shot to compensate psychologially for their gaze. And not that you could have siad, "Hey you! Could you move over a little bit?" but I think the shot would be even better with just the one girl.
This is a great setting and the shot is very interesting. I think it would be a challenge to make a visual statement in this place. I am glad you rose to the challenge; there is story here. This is like the entry-way to "Wonderland" in that Lewis Carroll novel about Alice. Or to the gateway to the Land of Oz and Dorothy is approaching in wonder. I like it. Maybe Myrddin is onto something; cropping it closer to show only one of the two young ladies would add some additional focus or storyline. I don't know, it might be worth trying sometime just to see.