In the past, the urban centre of S. Donato in Poggio was one of the principal fortified settlements of the zone. Worthy of the denomination castrum right from 1033, the castle was built high up on the hills separating the valleys of Val di Pesa and Val d’Elsa. The toponymy derives from the denomination of the church as registered in 989 with the name of S.Donato in loco Pocie. Pocie, and subsequently Poce or Poci, was therefore the name of the inhabited settlement, half of which was granted to the fief of the Guidi Counts by Enrico VI in 1901.

In the XII century, the S. Donato in Poggio castle enjoyed a certain degree of autonomy and became a free council. In 1218, the castle was definitively subordinated to the Republic of Florence, thereby taking on a considerable strategic importance due to its position on the most direct route of the Strada Romana, the one that linked Florence with Siena. The Florentines and the Siennese concluded a peace treaty at S.Donato in 1255 and the Florentine army assembled in this castle prior to the battle of Montaperti in which they fought the Siennese.

The Aretinian Ghibellines destroyed the medieval settlement in 1289. The only remains of the village fortifications from that period are perhaps the low part of the present-day municipal bell-tower. Reconstruction commenced immediately after the incursion and was financed by the Republic of Florence and by the parson Bernardo Gherardini. A high wall sustained the rampart. A tower and scarp without an internal wall at the major wall formed the two gates to the castle, one facing Florence and the other facing Siena. The ancient keeps or donjon within the inhabited area completed the defence structure. Before long, however, the development of trade and the lack of any further suitable building space within the walled castle area necessitated the development of a new settlement outside the Siennese gate, along the Strada Romana. Consequent to the administrative reorganisation of the country area surrounding Florence, S. Donato was appointed head of a League which covered the territory of three parish jurisdictions: S. Donato, S. Pietro in Bossolo and S. Appiano. A Podestà from the Florentine Republic governed this new administrative organisation.

The magistrature, situated in the town square, now known as Piazza Malaspina, was decorated with a XV century fresco, which may still be viewed. The building was reconstructed in large part after damage suffered during the last war. On the other side of the square were the public cistern, which was rebuilt in 1867, and the castle church dating from the XIV century. The late Renaissance facade of the Ticci Palace (which later passed over to the Malaspina family) united the houses and stores to the north and west of the square. In the village outside the castle, there was a hospital for the poor run by the Augustinian monks, and subsequently run by the St. Maria della Neve confraternity. The early years of the XV century marked the decline of the village. This was due to the greater importance gained by another route of the Strada Romana, which led from Sambuca up to Morrocco and passed through Tavarnelle and Barberino to reach the large centres of the Val d’Elsa valley.