La torretta di via Mazzini, unica superstite tra le ventotto torri minori che garantivano la difesa del circuito murario di Oristano, si trova oggi nel cortile di un’abitazione privata. Viene realizzata, unitamente alle altre opere difensive, per la munificenza del giudice Mariano II de’ Bas-Serra, tra il 1290 e il 1293.
La torre ha pianta quadra e mostra, in chiara lettura, la tecnica muraria impiegata in tutte le fortificazioni cittadine: una muratura a sacco in pietrame misto e malta, rifinita all’esterno con grossi blocchi in arenaria prelevati dalle cave locali. Si individuano variamente i risarcimenti operati nei secoli, come il rifacimento della copertura e le aggiunte in laterizi. Nonostante questi interventi, l’aspetto della torretta è rimasto quasi inalterato. In alcuni conci di arenaria sono ancora visibili le buche pontaie, ovvero i fori praticati lungo la muratura per alloggiare i travetti delle impalcature durante la costruzione della torre.
La torretta è visitabile in occasione di Monumenti Aperti.

Little is known about the presence of defensive town walls in Oristano during the late medieval age. Some documents dating back to 15^th century testify sections of old walls and solid buildings that are no longer recognizable in some renovated areas. During 1987, archeological research also revealed presence of a moat dug next to via Duomo, with elements connected to the Vandal domination of the Island. A true city wall was commissioned by the munificent judge Mariano II de’ Bas-Serra in the late 13^th century. Thanks to the dedicated epigraph of Porta Ponti and Porta Mari towers, it is possible to identify that these works were carried out in around 1290 and 1293. The huge fortification project completely redesigned the perimeter of the city, finally including 32 hectares. The solid perimeter walls extended for 2 kilometres, and comprised two mighty towers, together with their relative doors facing North and South, as well as two minor doors facing East and West, and 28 towers placed at intervals of almost 70 meters. The lack of information impedes the possibility of identifying who designed and constructed the walls. Comparison with a number of coeval fortifications in Iglesias and central Italy supports the assumption that the structures were probably built by local workers who followed Tuscan models, with the addition of independent elaborations and adaptations to meet specific environmental needs. It is possible to trace the path of the urban city wall thanks to plans made by engineer Rocco Capellino, who presented a project in 1557 to adapt fortification works in Oristano to meet the modern military needs imposed by firearms. The torretta di via Mazzini is the only presently surviving example among the 28 minor towers. It is currently located in the rear garden of a privately-owned house. It has a square base and presents the usual masonry technique used for the other urban fortifications: mixed stone and mortar rubble masonry with an external layer of sandstone blocks. Some external restoration was carried out over the centuries, such as the roof and additions in clay tiles, but other than this, the tower remains largely unchanged. Bridged holes placed along the masonry for scaffold joists during the tower’s construction are still visible in some of the hedging stones. Most of the city walls disappeared between the late 19^th and the early 20^th centuries, as a result of decisions made by the Council, which considered the medieval structures across the city a cumbersome and useless heritage that hindered progress. For this reason, the torretta now represents the only precious example of evidence from the past, and as such must be safeguarded and protected.