On the Napoleon road to the level of the strategic Baume cluse, Sisteron is protected by its citadel watching over the road between the Alps and Provence. Nestled at the foot of the fortress to which it is connected by an underground staircase, the historic part of the city consists of a maze of stairs and small vaulted streets called andrônes. They naturally follow its picturesque layering and are filled with mansions, carved doors, or plasterwork that the Little Train of the citadel allows visitors to discover through a commented tour.