Urbanization
The regular grid-plan of Roman Lutetia marked it as the city, in the Gallo-Roman sense. The city was the only sector in which, starting in the 2nd century AD, public monuments were constructed. 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 Roman public works were all on the north-facing slope of the hill of Ste Genevieve. 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. On the Left Bank, the Rue St-Jacques and on the Right Bank, the Rue St-Martin still follow the Roman main axis (cardo maximus).
An aqueduct 26 km in length, with a flow rate estimated at 2000 cubic meters a day, watered 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.
The amphitheatre, built into the slope of the hillside outside the city itself, is commonly referred to as Les Arènes de Lutèce. It was one of the largest such structures in Gaul.
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