A stronghold of the defensive border ‘belt’ of the Giudicato of Arborea, together with the Castello di Monreale in Sardara and the Arcuentu of Guspini, it played a fundamental role in the war against the Crown of Aragon. It is also said that Giudice Mariano IV stayed there and subsequently (perhaps) his daughter, the mythical Giudice Eleanor of Arborea, co-authors of the Sardinian legal code, Carta de Logu. The castle of Marmilla is a military fortress dating back to the times of the Giudicato, whose ruins rise in the territory of Las Plassas atop a hill that is 270 metres in height, perfectly conical and with a rounded shape, from which derives the name of Marmilla (as in, ‘mammillary’), a rich ‘land of wheat’. The castle was mentioned for the first time in a document dating back to 1172, the year in which it was ceded by the Giudicato of Arborea to the Republic of Genoa. Its origins date back even earlier, within the first half of the 12th century. It was the protagonist of the Middle Ages on the island, marked by protracted disputes. Following sa Batalla di Sanluri (the Battle of Sanluri in 1409), it became part of the Aragonese dominions, maintaining its defensive function for a century. Some rooms of the Castle, still in use during the feudal age, were then utilised as a prison until the 19th century.