The tower could overlook the entire gulf and keep in contact with the towers of San Giovanni di Sinis, Marceddà and Capo Frasca, as well as with Oristano and the neighboring villages. But its main function was to protect the mouth of the Tirso river, thus preventing it from being traveled to reach the city.
Initially called Torre del 'Puerto de Oristan' (1639), only in the Savoy Age did it take on its current name: 'Grande de Oristan', Torre d'Oristano and Gran Torre. It is the largest coastal tower in Sardinia, since it was originally designed as a 'Torre de Armas', that is, as a 'strong' tower, suitable for heavy defense. Although it began in the first half of the 16th century, the tower is of Aragonese design, as evidenced by the characteristics of the transitional architecture: from the masonry gate on the front door to the placement of the fire hydrants. It is equipped with upper barbetta gunships, that is, the uncovered battery, and with lower troniers, the slits, placed in the casematta, that is, the covered bombproof chamber.
Cylindrical in shape with a diameter of more than 20 m, it is spread over two levels: the first is about 8 meters from the ground, almost entirely destined for a large, vaulted chamber, where four large pieces of artillery were placed, pointed in various directions, both towards the river and towards the sea. The upper floor is circumscribed in the shape of a balcony to contain, through various troniers, other manually maneuverable firearms.
The construction began in 1542, after the orders of Charles V in 1535, with the use of money from the city of Oristano, but still in 1553-54 the Parliament complained about the slow work on the tower. It was then completed after 1555 thanks to the revenues linked to the right of anchorage that the city of Oristano obtained from the Viceroy. The completion of the work, however, must be placed before 1572, the year of Captain Campos' report, in which the tower was surveyed.
Despite being large and capable of housing a garrison of twenty soldiers and of supporting a siege of a few days, in 1637, in the middle of the Thirty Years' War, forty-two French sailing vessels, commanded by Admiral Charles of Lorraine, Duke of Hancourt, managed to land and plunder the city of Oristano for five days. Fifteen years later, in 1652, the Spanish government freed itself from the administrative burden of the tower, handing it over, together with the fish ponds of Cabras and Santa Giusta, to Girolamo Vivaldi. Restoration works were carried out in 1684 and others in 1692.
According to the report by Ripol, envoy of the Savoy king, in 1767 the tower was served by a garrison consisting of a warden (captain), an artilleryman and six soldiers; a number equal, at the time, to the tower of Bosa alone. Restoration work was documented in 1786 and throughout the 19th century there were reports of maintenance works, which guaranteed excellent architectural and static conditions.
The tower was used by La Marmora and De Candia as a geodetic point for the creation of topographic maps. Next to the fort, warehouses were built, which kept various merchandise. After the dissolution of the administration of the towers in 1842, it continued to be manned as a traffic light station. In the 19th century, in the Piazza d'Armi, 17 m above the ground, a neoclassical civil house was built for the farista.

Bibliography
E. Pillosu, The Coastal Towers in Sardinia, Cagliari, Tipography La Cartotecnica, 1957;
E. Pillosu, “An unprecedented sixteenth-century report on coastal defense by Marco Antonio Camos”, in New Sardinian Bibliographic Bulletin and Archive of Popular Traditions, V, 1959; F. Fois, Spanish Towers and Piedmontese Forts in Sardinia, Cagliari, La Voce Sarda, 1981; G. Montaldo, The Coastal Towers in Sardinia, Sassari, Carlo Delfino, Sassari Russo, 1992; F. Fois, Spanish Towers and Piedmontese forts in Sardinia, Cagliari, La Voce Sarda, 1981; G. Montaldo, The Coastal Towers in Sardinia, Sassari, Carlo Delfino, Sassari Russo, 1992;
F. Fois, Spanish Towers and Piedmontese forts in Sardinia, Cagliari, La Voce Sarda, 1981; G. Montaldo, The Coastal Towers in Sardinia, Sassari, Carlo Delfino, Sassari Russo, 1992; F. Fois, Spanish Towers and Piedmontese forts in Sardinia, Cagliari The defense coast of the Kingdom of Sardinia from the 16th to the 19th century, Rome, Army General Staff, Historical Office, 1992;
F. Segni Pulvirenti-A. Sari, Late Gothic Architecture with Renaissance Influence, Nuoro, Ilisso, 1994, sch. 21;
G. Montaldo, “Forts and Coastal Towers”, in The Fortified Architecture of Central-Southern Sardinia. Proceedings of the Study Day, Cagliari October 16, 1999;
M. Rassu, Guide to coastal towers and forts, Cagliari, Artigianarte, Cagliari 2000.