San Donato in Poggio still preserves some traces of the original city walls with their two gates. The town was mentioned for the first time in a document dating from March 1090. The following year, half of the village was granted by Emperor Henry VI to Count Guido da Modigliana, a member of the Guidi family; this donation was confirmed in 1220 by the descendants of Emperor Frederick II.
In 1218 the town became a possession of the Republic of Florence and its strategic importance began to grow, also due to its position along the road that connected Florence to Siena and Rome. Here the Florentine army gathered and was organized in expectation of the battle of Montaperti. After the battle, in which the Florentine Guelphs were defeated, the village and the surrounding territory were plundered by the Ghibellines. In the early 14th century, San Donato became the main seat of the league named for it, led by a magistrate sent from Florence.
The town is still surrounded by its 13th-century city walls. On the western side stands Torrino, an 11th-century watchtower of highly unusual shape. The town can be entered either through the massive northern gate, Porta Fiorentina, or the southern one, Porta Senese. The heart of the town is Piazza Malaspina, with a central octagonal well over a cistern below. The square is surrounded by the beautiful Palazzo Malaspina, dating from Renaissance times, the Church of Santa Maria della Neve and the Palazzo Pretorio.