One of the tower's first activities was to perform a function of customs and fiscal control of the area, as shown by the privileges granted by King Alfonso the Magnanimous in 1440. In the 17th century, up to and including the Savoy Age, the tower had functions of surveillance, control and, during the plagues, of prophylaxis of “suspicious” boats that could have spread possible epidemics.
The tower has an octagonal shape, very different from most of the island's classic cylindrical towers. The prismatic shape would denounce its Catalan origin and would be traced back to the model of the tower of Porcuna (Jaén), dating back to 1435. It is 16 m high and 15 m wide; each side measures 5.8 m; the base has a 1.8 m high shoe plinth.
The Port tower is spread over three floors: tank, accommodation, 7 m from the base, and terrace. The apartment has a circular perimeter with a support pillar in the center and the ceiling is made up of the combination of a stellar vault with a ribbed cruise. In the masonry of this room, you can see two troniers, a fireplace and two flights of stairs. Above, there is the gate and a system of protruding wall cores, supported by shelves.
The tower was built in July 1325 by Admiral Carroz, who had occupied Porto Torres with the Aragonese fleet. After building a first camp, he built a wall protected by a tower and a moat. At the same time, the new garrison was placed in the nearby castle of Monteforte.
Already in 1407, the Treasury had to ask for a loan to pay the guards of the Port Tower. In 1423, the King of Aragon, Alfonso V, promulgated the Royal Charter for the partial rebuilding and repair of the fortress. Subsequently, the tower lost importance, especially following the official transfer of the bishop from Porto Torres to Sassari in 1441. In 1487, by order of the viceroy, it was however rearmed and equipped with soldiers at the expense of the city of Sassari.
Between 1538 and 1553, there was the highest concentration of Barbarian assaults against Porto Torres and the relative demand, by Sassari, for a better defensive system. Still in 1583, in the seat of parliament, there were complaints about the lack of repairs to the tower. Only in 1628 were restoration works recorded. In 1637, inspections were carried out that noticed that the work had not been completed: the tower's parade ground was so cluttered with rubble that the gunner was unable to maneuver the mouths of fire in case of combat. In the same year, despite the fact that there were as many as 12 soldiers, the tower was occupied and damaged by the privateers of Bizerte, who also looted the Basilica of San Gavino. Finally, in the second half of 1637, restorations were carried out by master Cinquina; others were carried out in 1682, in 1694 and other modest works in 1720.
In 1761, the city of Sassari appointed the last “warden”, that is, the captain of the tower, following a custom that dates back to 1557, when Sassari had the privilege of assigning the position, in contrast to the royal appointment. In 1818, the office of warden was abolished.

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;
G. Montaldo, “Coastal Forts and 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.