Built in the second half of the 16th century, the Fortress of Girifalco was part of a plan for strengthening the defences of the State ordered by Cosimo I de' Medici. The fortress has a quadrangular plan, with bastions and gunners' posts inserted in the medieval fort (13th century), which is in turn built on the ruins of Etruscan structures. The fortified nucleus was in reality almost never used for military purposes because, after the war with Siena (1554-56), the Grand Duchy of Tuscan enjoyed a long period of peace. The fortress was purchased by the Commune of Cortona in 1770.