According to the humanist Lluís Pons d'Icart's description, in the 16th century the wall was 4,000 metres long. It completely surrounded the perimeter of the ancient town of Tàrraco, reaching as far as the port. Today only a fifth of it remains, in the upper part of the city.

Despite various hypotheses that the walls predated the Romans, recent archaeological research has provided conclusive proof that they were built by the Romans.

Two distinct phases of construction have been identified. The first dates from the initial years of Roman occupation and is four metres wide by six metres high. It was fortified with quadrangular towers of which we know three: the Minerva (or S. Magí) Tower, the Cabiscol (or Seminari) Tower and the Arquebisbe Tower. The second phase corresponds to a change in architectural and strategic thinking, possibly related to the military campaigns of the Consul Cato (beginning of the 2nd century BC). The width was increased to six metres and the height to twelve metres.

The same construction technique was used on the curtains and the towers. Large (megalithic) blocks of stone were used as a base for building a double wall of ashlars, normally bossed. The area between the interior and exterior paraments is filled with stones and soil in the base section and with adobe in the rest. The base of the wall has small openings (posterns) which allow access on foot.

Only one of the access gates remains today, that near the Minerva Tower, although this has been greatly modified over the centuries.

The military status of Tarragona throughout history has brought about repeated transformations and restorations of the walls, especially in the Middle Ages and during the War of Succession (1702-1714), when the British built the outer wall or "Falsa Braga". Dwellings with windows and balconies have been built in some sections of the walls, taking advantage of the space between the outer and inner paraments.