Castello di Villasor, Medieval castle in Villasor, Italy.

Castello di Villasor is a U-shaped fortified house arranged around a quadrangular inner courtyard, entered from Via Baronale through a round-arched portal bearing the Alagon Arborea de Silva coat of arms with a marchional crown. Its main facade has windows with carved Gothic-Catalan frames, and the walls are topped with Guelph merlons. Inside, two levels remain, one hall with a 15th–16th-century wooden coffered ceiling.

Giovanni Siviller, feudal lord of Villasor from 27 October 1414, built the fortress in 1415 on the remains of the old parish church of Santa Maria, with permission from the Archbishop of Cagliari. It was meant to defend the territory against incursions by Arborean rebels defeated in the war against the Aragonese. Through the marriage of Isabella, Giovanni's daughter, it passed to the Alagon family, and in the 18th century the Alagon and De Silva houses merged.

The crest above the main portal combines the Alagon, Arborea and De Silva arms, topped by a marchional crown. It recalls the 18th-century marriage of Manuela Alagon Arborea, marchioness of Villasor, to Giuseppe de Silva, which merged the two houses. The title of Marquis of Villasor and Grandee of Spain has belonged since 2009 to Álvaro Fernández-Villaverde y Silva.

The ground floor houses temporary exhibitions, conferences, civil weddings, and cultural events as a municipal property open to the public. Visitors should check ahead to learn about current activities or scheduled programs at the venue.

The upper-floor halls are currently closed to visitors, so the coffered ceiling of carved wood, dated to the 15th-16th century, cannot be seen from inside. The Guelph merlons along the wall tops and the curtain windows on the facade are visible from the street instead.