The original centre of the Colònia Faventia Julia Augusta Paterna Barcino was at the Mont Tàber but the city expanded during the Roman period. The Roman wall of Barcelona, built with big ashlars, was the defensive wall of the city until the 13th century. These remains of the Roman wall are the biggest monument in Barcelona. It has 76 towers and its fortified perimeter wall is 1270 meters long. The wall has been listed as Heritage of Cultural Interest. The archeological excavations carried out on site have exposed one third of the wall.

The area enclosed by the Roman wall is where the first Jewish community settled. The northwest quarter of the ancient grid of the city is where Jews lived.

The main axes of circulation of the ancient Roman city have been kept untouched in the streets of the Call in Barcelona. This grid has only had minor changes since ancient Roman times: carrer del Bisbe follows today the same route that the old decumanus maximus did. The Carrer del Call is where the ancient cardo maximus was and Carrer Sant Honorat is where the decumanus minor was. The axes between Marlet and Fruita follow the old cardo minor. The other streets like Carrer de Sant Domenec del Call follows what used to be the occidental decumanus minor and the axes formed by Santa Eulalia and Sant Sever follow the former northernmost cardo minor.

The section at Carrer del Call between Carrer de Sant Domenec and Carrer de Sant Ramon has a slightly different angle from the original Roman route: when Borrell II was the king, between 927 and 992, the fortification and the extension of Castell Nou Vescomtal (the Viscounts’ new castle) above the old Roman gate caused a slight diversion of the cardo maximus.

The most ancient remain of the city, an Iberian stele, was found by the Mont Tàber. (Cirici 2012: 304). The most important roman building in this area was the Roman Domus located where carrer de la Fruita is today. The remains found belonged to a majestic house of the 4th century and to several tabernae at the decumanus minor (Sant Honorat today). These buildings were planned and built together: it is believed that the domus and the shops belonged to a wealthy local man with enough power and resources to settle down by the forum of Barcino.

The Viridarium, the garden, has a lacus in the middle framed by a peristyle. Several cubiculum, a service area and a storeroom were built around this peristyle. Some polychromatic mosaics and frescos remain on the walls.