One of the over-riding factors ensuring the ease of Greek and Hellenistic civilisations' expansion throughout the Mediterranean basin, and the geographical factor which lent a cohesive potential to the Roman world was the Mediterranean Sea itself. During the 7th century B.C. it was the sea which provided outward access for the Greek colonial migration, and then later ensured communication between colony and mother city. The great weight which Greek colonists attached to securing an easy access to their maritime communication lines was a major consideration in determining the siting of the colonial cities. The increasing size of ships during the 5th–3rd centuries B. C. coupled with the vastly increased volume of maritime trade which characterised the Hellenistic period were major stimuli to the artificial development of those natural harbours on which the colonial cities were based.

Any study of classical harbours in Cyrenaica must begin with an examination of the literary sources of which two are particularly relevant. They are; the Stadiasmus Maris Magni (1), and Herodotus' account of the original Greek colonisation of Cyrenaica from the island of Thera (2). The Stadiasmus is a document to which at present no precise date can be assigned, but in its final form it is probably not later than the end of the 2nd century A. D., and it would seem to be a palimpsest. The Stadiasmus lists the harbours along the entire North African Coast from Alexandria to Tunis, and, being written by seamen for the guidance of seamen it is the equivalent of the modern Admiralty Pilot. The list of harbours which it provides indicates that there was a very strictly graded hierarchy of natural harbour types, for no less than six different nouns are used to describe harbour entities according to their geographical qualities. In the Cyrenaican section of the Stadiasmus nine harbours are listed which can be divided into three distinct groups according to the words used to describe them. The three groups are headed by the terms Euphormos, Hormos and Panormos in ascending order of merit, and each denotes a very specific type of natural harbour. The root word, Hormos, meaning a tore or collar, is used in a maritime context from the earliest literary times, and is so used by Homer. The various prefixes which are attached to the word, Euph and Pan, denote natural harbour types which either excel or in some way fail to match the norm, the Hormos. In its sense of ‘collar’ the word conveys a notion of the configuration of the ideal harbour, i.e. a land-locked bay to provide shelter for shipping with access to the sea.