The town of San Piero a Sieve is one of the favourite lands by the Medici. It is in the province of Florence ad it has a population of about 3,000 inhabitants. It stretches along the Mugello plan and is an affluent of the Arno, the Sieve river, sides it.

The Castle of Cafaggiolo, the Castle of Trebbio and the Fortress of San Martino are among the most important tourism destinations. Another extremely interesting is the convent of the Bosco ai Frati that, according to tradition was founded in the VI century. After being a property of the Franciscans in 1212, it became famous for housing the investiture of San Bonaventura as cardinal in 1273.
The legend tells that the pope arrived in the monastery just when the saint was doing out the kitchen. When he knew of the investiture, Bonaventura prayed the pope to wait until he had finished doing his housework before starting the ceremony. A Crucifix by Donatello is kept inside the monastery.
The town of San Pietro a Sieve has medieval origins. The first information on this centre in the Mugello dates to 1018. Yet, in the XII century, the town was still a small town that acted as an outpost near the bridge over the Sieve. The way to reach Bologna crossed the town. Originally, it belonged to the Ubaldini, before the Medici became its direct owners. Without any doubt, this Florentine family, who probably originated in the Mugello, provided the urban planning development of this area between the XIII and the XIV centuries.
The village of San Piero a Sieve extended under the Medici and increased its political importance in the Mugello. At the same time, its inhabitants started to understand its role as a crossroads. Thus, the first "hospitale" was born in 1275 and more were built on the road to Novoli in 1335 and in Tagliaferro.
Still in the XIV century, one of the masonry bridges over the Sieve was built. This event gave a further boost to the local trade and increased the importance of its postal station, crowded by the travellers on the Tuscan-Emilian road who wanted to change their horse.
In 1551, San Piero was put under the Vicariate of Scarperia. The construction of the fortress of San Marino, supervised by the Buontalenti, dates to the end of the XVI century. San Piero had always been in favour of the Medici and it was inevitably affected by the decline of this family. Also the destiny of the castle was influenced by the arrival of the Lorraine in Tuscany.
In 1774, Leopoldo I transformed the fortress into a village for the local farmers. In the XVIII century, the activities of spinning of flax and hemp joined the more traditional one, namely agriculture.