A common technique for composing a drawing is using a window or doorway to frame the scene. I particularly like using arched openings as a framing device since the shape is easily recognizable for what it is. Here are three examples, one of the Temple of Heaven in Beijing, another of S. Ivo in Rome , and the third from an old brewery building in Halifax, Nova Scotia.
In each case, I start with the shape and proportions of the arched opening. I then use this shape and size as the measure for everything that is seen and drawn within the arched shape. The arched shape also serves as the foreground element that establishes where I am and my relationship to what I am viewing.
Notice that I drew the archway leading to the courtyard and Borromini’s S. Ivo della Sapienza a little low but I didn’t let this prevent me from drawing the full height of its spire. This is a reminder to never let a framing device alter the proportions of what you are drawing.