The city is located N del Campidano and overlooks the Gulf of Oristano. The Tirso river flows nearby and there are the Santa Giusta and Cabras lagoon systems, at the end of a vast plain surrounded by the heights of Mount Arci. The territory documents the continuity of settlement from the pre-Nuragic age, with important archaeological evidence of the Phoenician-Punic, Roman and Byzantine presence. In medieval times it was the capital of the kingdom of Arborea, before being annexed to the Crown of Aragon. From the beginning of the 16th century it followed the general historical events of Sardinia, until it became the capital of the homonymous province in the 20th century.
The urban history of Oristano is closely linked to the events that occurred during the kingdom of Arborea, the last to fall under the Aragonese between the end of the 14th and the beginning of the 15th century. Oristano was the capital of the Giudicato, and as such it housed the sovereign, in his palace, and it also had to be equipped with an adequate fortified structure.
Even today, the urban structure of the city reveals its original nucleus: there are three points of confluence of the streets, corresponding to as many districts, precisely the current Piazza Roma in N, Largo Mazzini in N/E, Piazza Mannu in S. These three areas were crossed by walls, which protected the heart of Oristano: the wall had to be around 5 or 6 meters high, turreted, and started from the current Piazza Roma towards Via Mazzini, and then reached the tower of Portixedda; the walls continued to the current Via Solferino, Towards the square Mannu. In the latter, as in Piazza Roma, were the gates of the city, respectively the Porta Mari and the Porta Manna, namely the Tower of San Cristoforo (or Mariano's tower). Today, few ruins of the ancient walls emerge: a tower in Via Cagliari and some remains in Via Solferino, in the courtyard of the Boyl Kindergarten and in Via Mazzini. In the northern part, therefore, stood the tower of San Cristoforo, in the S part of the town the castle and the second tower, the tower of San Filippo, built to protect the castle and collapsed in 1872 due to the collapse of some vaults and walls. Like the tower of San Filippo, even of the castle, located near the current prisons, there is no trace left. It can be assumed that it was two-story and had rooms for servants and for troops.
Remnants of the fortified structure of Oristano are the Portixedda tower and that of San Cristoforo. Built like the rest of the fortifications in the Judicial Age and later rebuilt in the Aragonese Age, Portixedda comprises two overlapping cylindrical bodies, connected by an inclined truncated conical surface.
The tower of San Cristoforo or Mariano, a symbolic building of the Judicial City, was built in 1290 by the will of Mariano II, judge of Arborea. The tower, made entirely of sandstone, is a total of 28 m high, including 19 m from the base of the first round of blackbirds, while the smaller tower is 10 m high. With a square plan, it consists of two distinct and overlapping buildings. It has a “U” structure, with the open side facing towards the interior of the town, while the lower part of the tower, in ashlar ashlars, opens into a round arch that in turn opens into a pointed arch with a smaller diameter. An inscription was walled up inside the furnace, today in the Antiquarium Arborense, which, although very ruined, has served to date the tower to 1290; an altarpiece dedicated to Saint Christopher, from which the structure takes its name, was also kept in the tower.

History of studies
For the history of Oristano, see Francesco Cesare Casula's 1961 volume and Pinuccia Simbula's intervention in the 1990 miscellaneous volume. For the fortifications, see the extensive contribution of Foiso Fois in 1992 and the article by Raimondo Zucca in 1995. On the Mariano tower you can read Roberto Coroneo's card in the volume on Romanesque Architecture (1993).

Bibliography
D. Scano, History of Art in Sardinia from the 11th to the 14th Century, Cagliari-Sassari, Montorsi, 1907, pp. 388-390;
R. Carta Raspi, Medieval Castles of Sardinia, Cagliari, 1933, pp. 62-68;
Francesco Cesare Casula, Historical Profile of the City of Oristano, Cagliari, 1963; P.F. Simbula, “Oristano Judicial Capital”, in The Province of Oristano. The Footprint of History, curated by F.C. Casula, Milan, 1990;
F. Fois, Castles of Medieval Sardinia, edited by B. Fois, Cinisello Balsamo, Amilcare Pizzi, 1992, pp. 115-127;
R. Coroneo, Romanesque Architecture from the Mid Thousand to the Early 1300s, Nuoro, Ilisso, 1993, sheet 176;
R. Zucca, “The fortifications of the judge: in the Middle Ages Oristano was perfectly aligned with the urban planning criteria of the time”, in Sardegna Fieristica, 1995, without pages.