They demolished most of the old neighborhoods on the Île de la Cité, replacing them with a new Palais de Justice and prefecture of police, and rebuilding the old city hospital, the Hôtel-Dieu. They completed the extension of the Rue de Rivoli, begun by Napoleon I, and built a network of wide boulevards to connect the railway stations and neighborhoods of the city to improve traffic circulation and create open space around the city's monuments. The new boulevards also made it harder to build barricades in the neighborhoods prone to uprisings and revolutions, but, as Haussmann himself wrote, this was not the main purpose of the boulevards.[120][121] Haussmann imposed strict standards on the new buildings along the new boulevards; they had to be the same height, follow the same basic design, and be faced in a creamy white stone.