- The traditional text-led definition of Etruria into a league of 12 city territories (in fact, there are at least 14 larger cities), with a federal sanctuary (Fanum Voltumnae) is dedicated to Voltumna, supposedly located near Orvieto or Bolsena Lake. This is a frozen late definition of the political structure of Etruria. Some authors suggest that it may refer to the period between the fifth and third centuries BC. The league probably had more of a religious than political significance given the independence of individual cities, and its implementation may have been in response to the pressure of Rome. Some authors also suggest that the Etruscans in the Po Valley and in Campania were organized along similar lines. Candidates for membership among the Dodecapolis can be chosen from among the following cities: Arezzo, Caere, Chiusi, Cortona, Fiesole, Orvieto, Perugia, Populonia, Roselle, Tarqunia, Veii, Vetulonia, Volterra, and Vulci. The overabundance of candidates may, of course, reflect the fluidity of the political situation in Etruria, particularly with the advancing power of Rome, and the status of the 12 may have represented a frozen moment in time or an ideal representation of the situation that texts often reveal, rather than actual practice.
Historical Dictionary of the Etruscans. Simon K. F. Stoddart.