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an ancient city on the shore of the Black Sea on the site of the modern city of Sukhumi. Founded in the sixth century B.C. by Greeks from Miletus, Dioscurias traded extensively in cattle, salt, wax, bread, and slaves with Caucasian tribes. In the beginning of the first century A.D. it came under the control of Rome. During this period a fortress was built and garrisoned by Roman soldiers. The city began to be known as Sebastopolis. Dioscurias flourished in the second and third centuries A.D.; it began to decline from the fourth century. The fortress continued to exist, however, until the sixth century. Because of the sinking of the coastal region and inundation by water, the ruins of Dioscurias are now on the bottom of the Bay of Sukhumi.