The Latin word vicus was also applied to the smallest administrative unit of a provincial town within the Roman Empire, and to an ad hoc provincial civilian settlement that sprang up close to and because of a nearby official Roman site, usually a military garrison or state-owned mining operation.
Each vicus elected four local magistrates (vicomagistri) who commanded a sort of local police force chosen from among the people of the vicus by lot. Occasionally the officers of the vicomagistri would feature in certain celebrations (primarily the Compitalia) in which they were accompanied by two lictors.
These vici differed from the planned civilian towns (civitates), which were laid out as official, local economic and administrative centres, the coloniae, which were settlements of retired troops, or the formal political entities created from existing settlements, the municipia. Unplanned, and originally lacking any public administrative buildings, vici had no specific legal status (unlike other settlements) and often developed in order to profit from the presence of Roman troops. As with most garrison towns, they provided entertainment and supplies for the troops, but many also developed significant industries, especially metal and glass working. Some vici seem not to have had direct connections to troop placement (e.g., the Vicus Martis Tudertium).
Generally vici differed from the canabae. While the canabae were the extramural settlements of the major legionary fortresses (e.g. Eboracum, Vindobona, Durostorum), the vici were the extramural settlements of the auxiliary units (alae and cohorts).
Initially ephemeral, many vici were transitory sites that followed a mobile unit; once a permanent garrison was established they grew into larger townships. Often the number of official civitates and coloniæ were not enough to settle everyone who wished to live in a town and so vici also attracted a wider range of residents, with some becoming chartered towns where no other existed nearby. Some, such as that at Vercovicium (Housesteads), outgrew their forts altogether, especially in the 3rd century once soldiers were permitted to marry.