In 1207 a law was passed which made it obligatory for the podestà to be an outsider.
These cities bound them selves on that occasion not to acknowledge the author ity of emperor, king, duke, or marquis without the ex press order of the Roman Church.
At that time, in the interest of better administration, Florence abolished its old-time government by two consuls, and substituted a podestà , or chief magistrate (1193), with a council of twelve consuls.
About the same time they helped the Pisans in the conquest of the Balearic Isles (1114) asking no other reward than two porphyry columns for the great central doorway of the Baptistery (San Giovanni).
By 1155 they had grown so powerful that they dared to close their gates against Frederick Barbarossa .
The former was democratic, republican, favourable to the papacy ; the latter was the party of the old Florentine aristocracy and the emperor.
In 1197 the Tuscan League (in imitation of the successful Lombard League) was formed at San Ginesio between the cities of Florence, Lucca, Siena, Prato, San Miniato , and the Bishop of Volterra, in presence of papal legates.
After the introduction of a podestà it was exercised by the priors of the chief guilds (the artes majores ), seven in number (carpenters, wool-weavers, skinners, tanners, tailors, shoemakers, and farriers), to which were afterwards added the fourteen lesser guilds (the judges, the notaries-public, doctors, money-changers, and others).
To hold any public office it was necessary to belong to one or other of these guilds ( arti ); the nobles were therefore wont to enter their names on the books of the wool-weavers' guild.
The most famous of its few antiquities dating from Roman times is the amphitheatre known as the Parlagio .
In ancient times it was a town of small importance; its prosperity did not begin until the eleventh century.
In the eleventh and twelfth centuries the Florentines fought successfully against Fiesole, which was destroyed in 1125, and against several neighbouring feudal lords who had harassed the trade of the town, the Alberti, Guido Guerra, the Buondelmonti (whose castle of Montebuoni was destroyed in 1135), the Uberti, the Cadolinghi, the Ubaldini, and others.