The town was founded in the 5th century BC by Ancient Greek colonists who settled on the Chirakman Plateau in the colony Byzone (or Bizone). During the 3rd and 2nd century BC, the town played an important mediating role between the local Thracian settlements and the Greeks. Despite being unsuitable for wharfing because of its rugged cliffs, this part of the Bulgarian Black Sea Coast was an attractive centre due to the fact that the local people produced and traded with high quality grain.
During the second part of the 1st century BC the ancient town fell in the sea because of a disastrous earthquake. The frontal part of the Chirakman broke off and together with the richest citizens fell into the Black Sea's waters. According to the leader of the finished first part of the underwater archaeological expedition Kavarna 2005, Asen Salkin, the Roman town of Bizone has sunk two times in the sea. For that evidence the located form skin-divers borders of a sunk residential district of the town of Bizone in Kavarna's coast. For the presence of residential buildings the archaeologists judge by the found ashlars and parts of brick walls. The finds date from the 2nd century AD. According to the leader of the expedition this residential district has nothing in common with the disastrous earthquake from the 1st century BC. The underwater finds evidence for other phenomenon, for which the scientists express only suppositions, such as transgression and regression of the strata. It has started to transgress during the 1st century AD and this has continued to the 2nd century. It is possible that during this period the coast had risen by four metres and one day it suddenly fallen through.
During Roman times the town was restored under the same name and quickly flourished, the settlement revived and the port brightened up.
In the 7th century AD the Slavs and Asparuh's Bulgars destroyed the Byzantine town and later founded a new settlement, which entered the First
