Looking at the bigger picture and, we can never do this. We must use imagination to conceptualise the image... that we can do. Looking down ( or up ) at this Galaxy from a distant point of view at right angles to its plain. It would look like a large decathlon wheel with spiral arms and a central bar. Artists impressions are available.. check Wiki...? its there. Its rotating about its central mass and core. Local gravity influences the movement locally. We can not see a great deal of movement because we do not live long enough.