In 1855, work began on the north-south axis, beginning with Boulevard de Strasbourg and Boulevard Sébastopol, which cut through the center of some of the most crowded neighborhoods in Paris, where the cholera epidemic had been the worst, between the rue Saint-Martin and rue Saint-Denis. "It was the gutting of old Paris," Haussmann wrote with satisfaction in his "Memoires": of the neighborhood of riots, and of barricades, from one end to the other." The Boulevard Sébastopol ended at the new Place du Châtelet; a new bridge, the Pont-au-Change, was constructed across the Seine, and crossed the island on a newly built street. On the left bank, the north-south axis was continued by the Boulevard Saint-Michel, which was cut in a straight line from the Seine to the Observatory, and then, as the rue d'Enfer, extended all the way to the route d'Orléans. The north-south axis was completed in 1859.