The mountainous topography of the Greek peninsula resulted in the isolation of these two city-states.
Athens developed a system that valued philosophy and active political involvement by its citizens in an early form of democracy. (Note that it wasn't full democracy as we'd think of it today, as those who had a political voice were free men, not women or slaves.)
Sparta developed a militaristic system that valued physical training and military service, as well as a strict loyalty to the state.
Relatives to people who are already here is the answer in this question. People who are already in the country and earn much money to make their family lives immigrate to that country because their life will be stable. So the relative of the person who are already in that country is the reason why there has a large number of immigrants.
Technically, when people are attacked by their own government, or when they are denied equal access to education, it is the job of their fellow citizens to protect them, since the citizens should always rise up and demand justice when a government acts tyrannically.
