The north-south axis was dictated by the need to cross the marshy riverbanks in the shortest possible distance; several routes converged at the bridgehead.
The discovery of ancient paved roads, the established boundaries of the main monuments—the forum at the top of the hill, theatre, baths— even the path of certain medieval roads show that the Roman city was laid out with a module of precisely 300 Roman feet.
An aqueduct 26 km in length, with a flow rate estimated at 2000 cubic metres a day, provided the city with spring water collected from several points.
To bridge the Bièvre valley at Arcueil-Cachan, a bridge was required, whose piers and ruined arches, still discernible, gave rise to the toponym Arcueil.
It was Christianised in the 3rd century, traditionally when St Denis became the city's first bishop.
Under Roman rule, Lutetia was thoroughly Romanised with a population estimated at around 8,000.It is also shown in Asterix and the Laurel Wreath where it is mentioned as the greatest city in the universe along with Rome.Asterix and Obelix also make a brief stop in Asterix and the Banquet.However, archaeological discoveries between 19 strongly undermine the traditional location of the Île de la Cité for Gallic Lutece: the discovery of a large area of proto-urban urbanisation (15 hectares) on the current territory of Nanterre.In 52 BC, a year or so before the end of the Gallic Wars, the Parisii destroyed the bridges to the Île de la Cité.