Cities get divided by war, religion, politics, national boundariesor by all of the above. Often a smaller city may be nested within a larger city as in the case of Sun City within Phoenix, or Old Delhi in Delhi, India. While some divisions are peaceful, others are conflicted. For example, are there divides in culture and lifestyles? Do the two sides WANT a wall or not? How do people move across boundaries? How does the economy work? Maybe the poor on one side work for the rich on the other (as in South African cities, even today).