It is situated on the north-west coast about 25 kilometres east of the Gorditanian promontory, and on the spacious bay of the Gulf of Asinara.
Porto Torres' territory is situated on the north-west part of Sardinian Coast, inside the gulf called Gulf of Asinara. The extension of municipality is almost 10200 hectare and is suddivided in two parts with almost the same portion of land. One part is the part where is situated the city, the industry and the romanic ruins, the latter is Asinara island with the smaller Isola Piana. This part of territory is from 1997 a national park. The morphology of "city part" is flat, in fact Porto Torres and the rest part of north-west Sardinia is characterized by a Nurra flat, there are some hill formation in the middle of the flat, part of this hill formation is in Porto Torres' territory and the highest elevation of it is Monte Alvaro with it thickness of 342m. Furthermore the land territory is crossed by two rivers, Rio Mannu and Fiume Santo, the first draws the edge of Porto Torres territory on west instead the latter is pretty near the city and was used like a fluvial way from the Roman age.
In ancient times, Turris Libyssonis was one of the most considerable cities in Sardinia. It was probably of purely Roman origin, founded apparently by Julius Caesar, as it bore the title Colonia Julia. Pliny described it as a colony, the only on the island in his time, suggesting that there was previously no town on the spot, but merely a fort or castellum. It is noticed also by Ptolemy and in the Itineraries, but without any indication that it was a place of any importance.
The ancient remains still existing prove that it must have been a considerable town under the Roman Empire. According from the inscriptions on ancient milestones, the principal road through the island ran directly from Caralis (Cagliari) to Turris, a sufficient proof that the latter was a place much frequented. Indeed, two roads, which diverged at Othoca (modern Santa Giusta) connected Caralis to Turris, the more important keeping inland and the other following the west coast. It was also an episcopal see during the early part of the Middle Ages.
The existing port at Porto Torres, which is almost wholly artificial, is based in great part on Roman foundations; and there exist also the remains of a temple (which, as we learn from an inscription, was dedicated to Fortune, and restored in the reign of Philip), of thermae, of a basilica and an aqueduct, as well as a bridge over the adjoining small river, still called the Fiume Turritano. The ancient city continued to be inhabited till the 11th century, when the greater part of the population migrated to Sassari, about 15 kilometres (9 mi) inland, and situated on a hill. It was partly under Genoese hands before, in the early 15th century, it was conquered by the Aragonese. After the Spanish rule it was part of the Kingdom of Sardinia.
Torres was separated from the comune of Sassari in 1842. At the time the area which had been built around the basilica of San Gavino joined the fishermen's community near the port to form the new Porto Torres.
The port is connected by ferries with Genoa, Marseille, Toulon, Barcelona, Civitavecchia. Highway SS131/E25 to Sassari and Cagliari, and a national road to Santa Teresa Gallura (SS200). A railway operated by Trenitalia connects the town with Sassari, and the rest of the island.
Chemical industries support the modern economy of Porto Torres. Fiume Santo, a 1,040 MW power station owned by E.ON, is 5 to 10 kilometres (3 to 6 mi) west from the port, in the municipality of Sassari.
Plans related to industrial conversion are in progress in Porto Torres, where seven research centres are developing the transformation from traditional fossil fuel related industry to an integrated production chain from vegetable oil using oleaginous seeds to bio-plastics.