Semifonte was estabilished by Count Alberto IV of the Alberti di Prato family in 1177, in order to control the two main roads of val d'elsa.

As Podium Bonizi (Poggibonsi), its fortune was due to the possibility of contrasting the powerful Florence.

A new castle was very useful to the Alberti family to increase their financial and political power in Val d'Elsa.