Pen and ink wash is both an exercise in completion and in restraint. You have to be careful about what you end up emphasising. In my mind the water was the focus of this picture, but my contrast control needs some work. Also I didn't use rulers or vanishing points, and I only started using pencil a third of the way through. It shows.
My advice? Unless you are an architect and can do this in your sleep, pencil your damn architecture in first. Even when using a reference.