"Marcus is coming into the city now."
Translation:Marcus nunc in urbem venit.
Good point. Julius Caesar, BG 1.27, for instance, uses ad + accusative in the sense of approaching toward: prima nocte e castris Helvetiorum egressi ad Rhenum finesque Germanorum contenderunt, "they [the Verbigine] at night-fall departed out of the camp of the Helvetii, hastened to the Rhine and the territories of the Germanians." It wouldn't make sense that they hurried into the Rhine river.