The city was centered on the forum atop the Montagne Sainte-Geneviève between the Boulevard Saint-Michel and the Rue Saint-Jacques, where the Rue Soufflot is now located. The main building of the forum was one hundred meters long and contained a temple, a basilica used for civic functions and a square portico which covered shops. Nearby, on the slope of the hill, was an enormous amphitheatre built in the 1st century AD, which could seat ten to fifteen thousand spectators, though the population of the city was only six to eight thousand.[21] Fresh drinking water was supplied to the city by an aqueduct sixteen kilometres long from the basin of Rungis and Wissous.