The town of Castelfranco di Sotto rises on the right bank of the Arno in the province of Pisa. It has a population of about 11,000 inhabitants and it is rich in monuments such as the church of San Lorenzo Martire, the Villa Campanile of the XVIII century and the Collegiata of San Pietro of the XIII century.

The origin of the village is usually dated to the XII century, but its fortification dates to one century later. After the decadence of the Cadolingi, the feudatories of the area, the territory passed under the seigniory of the Lucca that settled the building of the first walls. The parish of Santa Maria a Monte was the main point of reference for its future inhabitants since it controlled many nearby villages, namely San Pietro a Vigesimo, San Michele in Caprugnana, San Bartolomeo a Paterno and San Martino in Catiana.
The origin of Castelfranco's toponym is to be attributed to the town's main function, that is to say to host the inhabitants of the nearby towns that had been devastated by the invasions of the bandits and by the fights between Pisa, Lucca and Florence or between Guelfs (who supported the church) and Ghibellines (the supporters of the empire). Moreover, Lucca had a great interest into having a defensive bastion along the border with Pisa. Thus, the "free" castle was born and "free" meant open to anyone wanted to build their house and start an activity here.
Despite keeping its structure of Roman "castrum", which is still visible today, the centre was surrounded by huge walls where four doors were opened and sixteen towers were raised. This impressive defensive complex was tested to the limit during the XIII and the XIV century, when the leaders Guido Novello, Uguccione della Faggiola and Castruccio Castracani attacked it. During this troubled period, Castelfranco alternatively belonged to Lucca and Pisa, until it created its autonomous and independent political administrations.
After 1330, the presence of the Florentines consolidated in the Valdarno since the town submitted to it spontaneously and benefiting a lot from it. In 1333, for instance, a enormous flood of the Arno destroyed its walls and the Florentines rebuilt them in 1424. in the XVI century, the definitive annexation of Pisa to Florence took place and Castelfranco began a period of peace and prosperity and under the already re-establised dominion of the Tuscan Grand Duchy. Trade and river navigatin increased turnover of the ton that soon became a Town Hall and, therefore, an autonomous "comunitas" in 1774. Castelfranco enlarged its territory up to its current dimensions with the Unity of Italy to which it annexed in 1859.