Paris has its origins around the Seine. Since the Neolithic period, people have occupied its banks, as evidenced by the dugout canoes and the remains found at Bercy. From the Middle Ages to the 17th century, the Seine was the main supply route for Paris and ensured its economic potential. In total, thirty-seven bridges cross the Seine in Paris, most of them built during the 19th and 20th centuries. Some are real works of art (Alexandre-III bridge), others take the metro from one bank to the other (Bir-Hakeim bridge). The oldest is the Pont-Neuf (1578-1607), while the Pont de la Concorde was built with stones from the Bastille prison.