The forum is one of the most characteristic buildings of the Roman city. It normally consisted of a large plaza surrounded by arcades and a series of buildings (basilica, temples, curia, tabernae, etc.). Here, the majority of public activities involving politics, the law, religion and commerce took place.

Tarraco, as capital of the Province of Hispania Citerior in Imperial times, had two forums. One was located in the Upper Part of the city and was reserved for the Provincial Council. The other was used for local affairs and was in the Lower Part, near the theatre and the port.

We have a partial knowledge of the Colonial Forum. Of the preserved remains, the most significant is the basilica, a building of three naves with an ambulacrum or perimeter passageway around an arcade of 14 x 4 columns with annexed premises. At the axis of the building there is a large hall paved with marble. This would have been the seat of the tribunal and also possibly the curia (the meeting hall for the city council), presided over by a statue of the Emperor. On each side of this hall there is a series of small premises, used either for business or the meetings of religious fraternities (collegia).

The basilica adjoined to the forum plaza which extended to the south, beneath the present-day Gasòmetre and Caputxins Streets. A narrow passageway, with a drain covered by large stones, separates the basilica from a small plaza adjoining the Forum, with the foundations of what was probably a temple.

A paved street leads from this plaza. It has a curb and a sewer running below it and connects with other perpendicular streets that delimited blocks of houses.

A large number of statues have been found around the basilica, some of which are related to the Imperial cult. In the plaza adjoining the basilica various statues of members of the Julio-Claudius family (27 BC - 68 AD) were found.

The wealthiest citizens also placed statues in the Forum Plaza, and sometimes even inside the basilica.

Inscriptions found in that area lead us to believe that the Tarraco forum already existed towards the end of the Roman Republican period.

The remains we can see today, however, are from a later remodelling during the first half of the 1st century AD.

The Tarraco forum was destroyed by fire shortly after the year 360 AD, possibly during a Barbarian incursion.