The Black Sea and the Bosporus border it on the east. The southern boundary is formed by the Sea of Marmara, the Dardanelles, and the Aegean Sea. The Adriatic and Ionian seas lie on the west. Most of Romania is not a geographic part of the peninsula. But, as a whole, it is often considered a Balkan country because of its close ties with the region in history and politics.
Mountains cover much of the peninsula.
The Dinaric Alps extend through Croatia along the Adriatic Sea to Greece, where they are called the Pindus Mountains. The Balkan Mountains stretch from the eastern border of Yugoslavia across Bulgaria. The Rhodope Mountains rise in southern Bulgaria. The Danube River is the area's chief commercial waterway. Other important rivers are the Morava, Vardar, and Maritsa.