The Greek city-states which developed starting 1100 BC were done independent of each other yet still had common characteristics which were shared. In city-states such as Athens and Sparta, you will find a similar way of life and structures, however each city-state did differ due not only to differing cultural origins, but also because of the geography Greece.
The origins of some of the city-states can be dated back to 1100 BC when the Dorian tribes invaded the Mycenaeans from the north. Some of the Mycenaeans, also known as Achaeans, sought refuge in Attica, where they mixed with the existing civilization to eventually form the city-state of Athens. The Dorian invaders took over the southern valleys of Peloponnesus where they settled in the valley of Laconia, which later became to be known as Sparta. These early societies had a lot of influence from Indo-European culture, as well had developed a political system similar to the ones the Mycenaeans had in place. These city-states however developed a variety of unique political systems from each other by 700 BC.
The reasoning for the development of differing political systems between the city-states can be attributed to the geography of Greece. The geography of Greece contains a lot of mountains hence travelling inland was very difficult. Due to this the city-states were not able to properly communicate with each other, which made political unification between the city-states extremely difficult. As well if it were not mountains dividing the city-states it would have been water, such as the Gulf of Corinth and the Mediterranean Sea. Although being accessible to each other by sea more so than inland travel, these factors would slow down communication leading to the development of separate political systems and cultures between the city-states of Greece.
Yet because of the geography and the Mycenaean influences on the city-states there were similar characteristics between them. The warm climate of the area resulted in the people spending more time outdoors, as well due to an abundance of rocky hills; olives and grapes were the main choice of harvest in their culture as they grew easily on those lands. As a result of a lack of inland travel due to geography, the independent communities of the city-states would each consist of an agora, which was a market place, as well as an acropolis, which was a fortified citadel built on a high rocky place where the people could place shrines for gods. There also resulted in a tribal king, who would rule each city-state, some city-states would have a hereditary monarchy while others would elect their king. Since the population of each city-state was small, all male citizens were encouraged to participate in the government of the community, the founding grounds of Greek democracies.
Even though the evolution of the city-states differed from each other due to factors such as cultural influence, and the geography of Greece, it was the same factors, which also produced the somewhat similarities between the city-states. Geography restricted the amount of inland traveling, which resulted in the development of city-states independent to each other, however it was the common climate and the common influence of the early Mycenaean culture that resulted in the common cultures of the great city-states of Greece.