Made to celebrate the centenary of the Galleria, the film traces its history from Giuseppe Mengoni's design, with its architectural and lighting wonders (gas flames), to its destruction during the war and its reconstruction in the post-war period. Olmi focuses mainly on the Galleria at the time the film was made, the crowds that inhabit it, the passers-by, the loiterers, the groups of anonymous gesticulating figures, the customers of bars and clubs, the nighttime crowd that appears there at dusk, the garbage collectors, the workers and immigrants looking for work who cross it at dawn.