The Mediterranean Sea is connected to the Black Sea through the Turkish Straits system, which includes the Dardanelles Strait, the Sea of Marmara, and the Bosporus Strait. The Dardanelles specifically connects the Aegean Sea (part of the Mediterranean) to the Sea of Marmara, which then connects via the Bosporus to the Black Sea. This waterway has been historically crucial for trade and military strategy.