Professor Zoom wrote:
Actually, that rock is quite clearly the one in Central Park. In fact, all of the stuff in the park is quite clearly Central Park. The fountain, the area where Rory is taken, the bridge, all of it. It's Central Park.
And could have been shot in Cardiff with the background CGI'd in (like they did in plenty of other shots in the episode.) They only reason they went is Moffat's obsession with appealing to the tiny American audience.