In ancient Greece, government structures differed significantly between city-states. Athens is often characterized by its development of democracy, where citizens participated in decision-making. However, it did have oligarchic phases, particularly during times when a select few held power.
On the other hand, Sparta was ruled by a mixed government that included elements of oligarchy, as it was controlled by a small group of elite citizens (the gerousia) and two kings, alongside a broader assembly that had limited power.
Given this context, the government system of Athens was primarily democratic, while Sparta is more closely associated with oligarchic tendencies. Therefore, the most accurate response would be "Sparta."