The boundaries between communities are determined by many factors, from race to location. One factor that I believe describes the boundaries between communities is social class. Social class is the difference between the rich and elite, the poor and disenfranchised. Such adjectives are what subject communities to perimeters.
You don't even need to stroll through to a rich area to see or feel the air of being off limits. Just turn on your TV and become witness to the luxurious lifestyles of the rich. Communities filled with mansion-like estates ranging from one million dollars to one billion dollars plus, enriched with gates and high-class security. These rich communities are located near the best areas of the star- near the beaches, high class stores, et cetera- so as to be convenient for the wealthy. These conveniences are easy to obtain since they have the means to do so, therefore these areas have a lower percentage of crime. The top notch security sees to the relatively low crime rate.
Now, seeing the lesser parts of society is a bit more harder, seeing how the lifestyle of the less fortunate is a bit depressing, but it can be found. How to describe the lifestyle of the poor and desperate? Well, for one thing it is home to poverty, the exact opposite of luxury. There is no high- class security, oh no. These neighborhoods are filled with the people the rich need to be protected from. Not to say that the poor is only composed of criminals, only that the cycle of crime repeats itself due to the inability to get themselves out of that situation.
How does this pertain to the boundaries between communities? The differences between social classes equates differences, and therefore, boundaries between communities. The upper class communities is made virtually inaccessible, literally and metaphorically, due to strong security and the need of a very generous salary. To the poor, or anyone who doesn't have a large salary for that matter, these restraints builds the impassible borders that surrounds communities defined by social class.
Just as the upper class communities are restricted to the poor, so too are the lower communities restricted to the upper class. The wealthy status of the upper class limits them to high-priced areas. Stepping into a lower class neighborhood is like committing suicide, it is ill advised. Many would feel unsafe in such communities, restricting them to their own neighborhood and a limited circle of friends. These factors not only set up boundaries for each community, but also keeps society segregated.