Casteddu Etzu, Medieval castle in Cuglieri, Italy.

Casteddu Etzu, also called castello del Montiferru, stands in ruins on a phonolitic trachytoid hill in the Montiferru massif within Cuglieri, province of Oristano. Its elongated plan enclosed rooms whose foundations remain, along with stretches of wall, tower remnants and underground chambers probably used as cisterns.

Ittocorre di Gallura, brother of Judge Barisone II of Torres, built the castle in 1186 to protect the kingdom's border against the Judicate of Arborea. In the 13th century, after the Judicate of Torres disappeared, Mariano II of Arborea annexed it with the surrounding lands. From 1410, under Aragonese rule, it lost its defensive role and changed owners several times until its abandonment in 1670.

Locals call the ruin Casteddu Etzu, "old castle". Its fame comes from Francesca Zatrillas, countess of Cuglieri and marchioness of Siete Fuentes, who took refuge here in 1668, suspected of her husband's murder and of complicity in the plot against viceroy Camarassa. Warned that a commissioner was coming to Oristano to pursue her, she fled at night to the rural church of San Lorenzo, then reached the cove of Foghe and sailed for Livorno.

The ruins lie about three kilometers from Cuglieri town center and are reachable via the provincial road connecting Montiferru with Marghine. Wear comfortable shoes and bring water, as the area is open and sunny.

The castle's fame comes from Francesca Zatrillas, marquise of Laconi, who took refuge there in 1668, suspected of arranging her husband's killing and of involvement in the plot against viceroy Camarassa. Warned that a commissioner's horsemen had reached Oristano, she fled at night to the rural church of San Lorenzo, then made her way to the cove of Foghe and sailed for Livorno. The fief returned to the Crown and the castle was abandoned from 1670.