San Giovanni Valdarno was re-established from 1296 under the name “Castel San Giovanni” by the Commune of Florence as a so-called Terra nuova (fortified new town). The place served to secure the border between the Republic of Florence and its neighbor Arezzo upstream of the Arno, as well as a fortified marketplace and customs post on the pilgrimage and trade route Via Cassia to and from Rome, about a day’s journey from the mother city .

The Castel San Giovanni was the prototype of a series of five new town foundations by the municipality of Florence, which, from the turn of the 14th century, pursued the goal of fortifying the still young territorial state on its periphery. In the following years until 1348, Castelfranco di Sopra (Valdarno), Scarperia (Mugello), Firenzuola (Apennines) and Terranuova Bracciolini (Valdarno) were founded according to the same type.

The urban planning type of these medieval planned cities is characterized in particular by the strictly right-angled city floor plans , which are spanned symmetrically around a central longitudinal axis. The mostly rectangular (San Giovanni, Scarperia, Terranuova), sometimes almost square (Castelfranco di Sopra, Firenzuola) “castles” were surrounded by a city ​​wall with towers . The gate towers, which today only survived in individual cases in the medieval substance, were each located in the middle of the four walls, were specially dedicated to patron saints and cited the architectural forms of the gates of the mother city of Florence as stately landmarks.