Greece is made up of two peninsulas. The Peloponnese peninsula and the mainland are joined by the Isthmus of Corinth. Eighty percent of greece is mountainous. There are many plateaus and river valleys in Greece but the defining feature and what also separated the greeks are the mountains which caused many different life styles. The sea changed the greek culture by enhancing their trade. Nowhere on the peninsula did the greeks settle more than 60 miles from the sea. The three seas around Greece are the Aegean, Mediterranean, and Ionian Seas, because of this the greeks became good seafarers.