Later, in medieval times were extended by the Aldobrandeschi and further fortified by the Orsini in the Renaissance period, when he commissioned the Florentine architect Antonio da Sangallo the Younger to give a more impressive structure of the entire defensive perimeter.
Roccalbegna is home to several notable fortifications, such as the Cassero Senese (built in the 13th century by the Aldobrandeschi, renovated in the 15th century) and the Rocca Aldobrandesca, located on the hill overlooking the town and the Albegna river (whence the town's name).