An early medieval commune, Cascio was later controlled by Lucca and included in the Vicariate of Gallicano; it was a forced passage between Garfagnana
and Lucca on the route across the pass of Monteperpoli. In 1429 it passed under the Dukes of Este and was included in the newly established Vicariate of Trassilico
; this enhanced its strategic importance on the border with the territory of Lucca. Its ancient fortifications, simply a thin wall surrounding the village, were insufficient against the threat of artillery; however they were only revamped after the war of 1613 when the inhabitants of Cascio, who had surrendered to the enemy during a siege, were accused of treason as soon as the authority of the House of Este was re-established and accepted the burden of fortifying the entire village at their own expense to escape being hanged. Work on a stately project by Pasio Pasi, later further extended, at an estimated cost of 18000 scudi, began in 1615.