Callatis was founded on the north-western shore of the Black Sea, on an isthmus between the sea and a lake. Powerful arthquakes have sent much of the ancient city’s eastern part beneath the waters. It is assumed that the city was originally called Acerbatis or Cerbatis. Known forms of the toponym are Kallatis and Callatis, as written in Greek and Latin manuscripts and stone carvings. From the late 14th century, in Italian portulans and documents referring to inshore navigation, the names Pangalia, Pankalia, Mangala and derivatives are attested, later coalescing into the current Romanian name of Mangalia.

Callatis was founded as a colony of Herаklea Pontica, with the first mention of it relating to a revolt against the Thracian King Lysimachos in 313 BC. After the revolt had failed, part of Callatis’ approximately 1000 inhabitants left the besieged city by sea to settle in Chersonesus near modern-day Sevastopol in the Crimea in what was the kingdom of Bosporus. The remaining citizens began trading and governing themselves jointly with the local populace.

In 260 BC Callatis and Histria waged an unsuccessful war on Byzantium for economic dominance over the neighbouring city of Tomis (Constanţa). From the latter half of the 4th century BC Callatis made significant social, economic and cultural advances which endured for the rest of the Hellenic period. As the many amphoras, ceramics and coins imply, the city traded with its hinterland and also by sea with, inter alia, Heraclea Pontica, Sinope, Athens, Rhodes, and Thassos. The minting of bronze, silver and gold coinage began in the late 4th century BC, continuing until the middle of the 1st century AD. Coins bore Greek inscriptions and the image of thе city’s patron god Heracles, as well as those of Dionysus, Apollo, Demeter, Cybele and other deities.

Source: http://samos-webcms.aegean.gr/mediawiki/index.php/Kallatis