A municipium (pl. municipia) belonged to the second highest class of Roman cities, being inferior in status to the colonia. The first municipium was Tusculum. The distinguishing characteristic of the municipium was self-governance.
The citizens of municipia of the first order held full Roman citizenship and their rights (civitas optimo iure) included the right to vote, which was the ultimate right in Rome, and a sure sign of full rights.
The second order of municipia comprised important tribal centres which had come under Roman control. Residents of these did not become full Roman citizens (although their magistrates could become so after retirement). They were given the duties of full citizens in terms of liability to taxes and military service, but not all of the rights: most significantly, they had no right to vote.
Executive power in municipium was held by four annually elected officials, composed of two duumvirs and two aediles, all under the thumb of Roman rule. Advisory powers were held by the decurions, appointed members of the local equivalent to the senate. In later years, these became hereditary.
Kenrick further went on to note that the distinction between colonia and municipium "are hardly applicable to Britain", observing that "I am not aware that any inscription exists, in which the name of municipium is given to a town in Roman Britain". In fact, the evidence for Verulamium being a municpium comes not from an inscription but from book 14 of the Annals of Tacitus.