Archeology and written sources seem to confirm the traditional idea that the Roman Corduba was founded in the mid second century BC by General Marcus Claudius Marcellus, after a long period of coexistence among colonists and troops with the old indigenous settlement located on Colina de los Quemados (current Parque Cruz Conde).
The new Corduba chose for its location a natural terrace easily defendable. Placed about 750 meters northeast of the Turdetan nucleus, and separated both by several waterways that flowed into the future river Baetis, this new settlement gradually polarised the population of the area, which finally caused the abandonment of the old Turdetan oppidum. The new city, which mints its first coins with the legend Corduba around about the years 80-79 BC, rapidly prospered thanks to trading, to the agricultural valley resources, to the control of the river port, as the river was navigable to its very gates, and especially to the mining wealth of its mountain, which funds the conquest and favors the enrichment of the first cordubenses family lines.
At the beginning, the Republican city occupied only the top of the hill that still forms the center of the modern city. It is an essentially flat surface, protected by pronounced slopes except on its northern side (where a defensive moat of great width and depth was disposed), and by the channels of several streams. Its planning follows the characteristics of Italic urbanism, with a walled perimeter provided with towers and a regular urban road network governed by the kardo and decumanus maximums, oriented to the four cardinal points, and organized in blocks (insulae) of 2 by 2 actus (that is to say, 70 x 70 meters). As a singular element, the new Corduba had two decumani maximi, one of which was the entrance to the walled enclosure in the East, and another was the way out towards the West. This solution was probably aiming to reinforce the iconic character of the space reserved for the forum. The first formal paving of streets, the installation of an effective sewers network and the first monumentalization of houses and public buildings have not been archaeologically detected until the early first century BC. Until then the city would have maintained a certain camp aspect, with buildings mainly built in stone, wood and mud.
In the mid of the 1st century BC Corduba fell into the hands of Caesar and his army. They did not forgive the partisanship of the city to the Pompeian side, so they destroyed it and executed twenty thousand of its inhabitants.
After years of recession, the battered city would be refunded (it has been traditionally thought that by Augustus himself, although there is no unanimity about it) with the status of colony. This brought the full Roman citizenship to its inhabitants, and a new patronymic that would be maintained only some centuries: Patricia. As the capital of Baetica, the most prosperous province of the West, the city expanded its urban area towards the south, to the very edge of the Baetis. For achieving this, the southern front of the republican wall was dismantled, increasing the intramural space to about 78 hectares. This new fence would have several doors, some of them monumental, such as the one located under the later Gate of Gallegos, in the western front, or the one that opened directly to the bridge.
From this moment, the new Colonia Patricia began an intense program of urban monumentalization following models imported from Rome. This can be seen in the construction of large buildings and the systematic use of noble materials such as marble; the reorganization of the road network and the provision of better services and infrastructures, including an efficient system of sewage disposal under streets paved with puddingstone; or the enlargement of the cardo maximus. This was a great avenue that crossed the town from north to south, which was twenty meters wide adding the width of the driveway and the side porches. Similarly, the former Republican Forum was paved with gray limestone slabs and surrounded by porticos and important civil or administrative buildings, such as the basilica, the curia or tabularium. There are no direct archaeological evidences of them, although the finding of various architectural and sculptural elements, oversized, confirm their presence, also related to the transcendental functions that the capital of the new province Baetica must have developed.