Original: The boundary between Asia and Europe is conventionally considered to run through the Dardanelles, the Sea of Marmara, the Bosporus, the Black Sea, the Caucasus Mountains, the Caspian Sea, the Ural River to its source, and the Ural Mountains to the Kara Sea near Kara, Russia.
Simplified: This boundary runs North-South down the Ural Mountains in Russia, along the Ural River to the Caspian Sea, and through the Caucuses Mountains to the Black Sea.