A wall can be a barrier. It can be a structure of limitation or a source of repression. For the Inside Out Project, a wall is a canvas, and so are sides of trains, the arches of bridges and the steps leading to Brooklyn brownstones. This fascinating documentary tracks the evolution of the world’s largest participatory art project, the wildly popular Inside Out. From Haiti to Tunisia, South Dakota to the streets of Paris, French artist JR motivates communities to define their most important causes by pasting giant portraits in the street, testing the limits of what they thought possible. The power of paper turns people who feel without voice into unlikely activists by empowering them with their own images.

• Documentary