The fortress town of Callatis (surnamed "The One with Strong Walls") was founded at the end of the sixth century B.C. by Dorian Greek colonists come from Pontic Heraclea (today Eregli, Turkey). This Heraclea was said Pontic in order to tell it apart from another Heraclea in Sicily. Besides Callatis, Pontic Heraclean colonists also founded another famous fortress on the peninsula of Crimea (also at the Black Sea), namely Chersones, name that seems to be meaning nothing but Peninsula.

Pontic Heraclea being a city built at its turn by colonists come from Megara, and Megara being founded by the legendary Herakles (Hercules for Romans), the citizens of Callatis deemed the great hero as their ancestor. Today on very place of Callatis lies the Romanian municipium of Mangalia.

Along many other Greek cities, Callatis was part of the great coalition rounded against the Romans by Mithradates VI Eupator (132 - 63 B.C, ruler from 120 B.C. to his death).

The city fell to the influence of the great Dacian king Burebista betwix 50 B.C.. Licinius Crassus, in 29-28 B.C., seizes definitively the city inside the borders of the Roman Empire.

Callatis was member of the Pontic city community, federation known as Hexapolis. The other five member cities were Tomis, Histria, Dionysopolis, Odessos and Mesambria. The declared purpose of the community was celebrating the cult of the emperor, but likely there was more to it. Capital city was Tomis and the federation president was called pontarch.

Callatis suffered severely from the barbarian invasions. In 269 A.D. the city resisted heroicly against the barbarian coalition led by the Goths. The city lost only the suburbs lain outside city walls, that were burnt.

The first coins struck by Callatis were silver drachmae in the fourth century B.C., some bearing on the obverse the head of Herakles (mythical ancestor of the Callatian Greeks) and on the reverse his feared weapons: the club, the bow and the arrows envenomed in the blood of the Lernian Hydra. During the first century B.C. coin striking ceases. Callatis strikes again from the beginning of the second century A.D., until the reign of Philip Arabs when striking was over for ever.