The elements generally overlap and don't exist in isolation. Massachusetts Institute of Technology and the President and Fellows of Harvard College. 1960. 23rd printing, 1994.
People observe the city while moving through it.
People enter the city at strategic points, or they head toward a spot. Edges close one region from another. Or, they could be lines that hold related regions together. Districts are the sections of the city. Landmarks become identifiable if they stand out and are different from their surroundings.