Final answer:
Athens had the geographical advantage in terms of naval power and sea trade control, while Sparta had the advantage in land-based military strength. The Peloponnesian War showed that Athens' strong fortifications could hold off Spartan attacks, but Sparta was superior on land.
Step-by-step explanation:
Between Athens and Sparta, the matter of geographical advantage is nuanced. Athens, with its control of the coasts and islands of the Aegean, possessed a powerful navy and used its superior seafaring abilities to bring in supplies and move around its troops. Meanwhile, Sparta was a land-based power with a strong army, adept at land warfare. In terms of defense, Athens was well-fortified and difficult for the Spartans to conquer despite their military strength. Sparta, on the other hand, was head of the Peloponnesian League and exerted influence over a wider area of the mainland.
Athens's geographical advantage mostly lay in its ability to control trade and supply lines via the sea, whereas Sparta's advantage was in its land-based military power. The long-lasting conflict between these city-states, known as the Peloponnesian War, demonstrated that while Athens could hold off Sparta with its strong walls and navy, Sparta had the upper hand on land.