This study focuses on the architectural landscape of the lower Valdarno area, which formerly belonged to the diocese of Lucca and in the 17th century formed the new diocese of San Miniato. Despite the distance from the Bishop, Lucca managed to keep the ecclesiastical jurisdiction of this area until the modern era, while, from a political point of view, these territories gravitated towards Pisa and Florence. Historically and politically this area has been rightly described as a "borderland", disputed between the most powerful cities of Tuscany and characterized by an anomalous overlapping of jurisdictions. Similarly, in the cultural sphere, and specifically in the architecture, the geographic location and the changing political events, led to a great variety of cultural and stylistic references, which were combined creating an interesting blend of styles. Unfortunately, the total number of churches that have preserved medieval structures is quite low, especially when compared with that of the religious bodies listed in the documents of the late 13th and early 14th century, such as the Estimo of the Diocese of Lucca and the Rationes decimarum Italiae. From these sources we gather that there were 26 parish churches and a total of 154 religious buildings among churches, rectories, hospitals and monasteries, which means that this was one of the most populated areas of Tuscia during the Middle Ages.