Standing on a rocky spur, Triana Castle guards the passage between the Poderone and Chiesacce ditches. Despite being cited in 760, the castle was only documented in 1216 when its ownership was transfered to the Santa Fiora branch of the Aldobrandeschi family. Enclosed by a fortification which is accessed by a single door in the walls, the ancient medieval castle was ceded to the Piccolomini in 1388 before being transformed into a rural seigniory in the 16th century. Inside the walls, there is a chapel built by Lelio Piccolomini, which was renovated in Baroque style in the 18th century, surrounded by an Italian hanging garden. In 1962, the castle was sold to the Sienese company Pie Disposizione.