Pablo Picasso's 'Guernica' is perhaps the most famous anti-war painting in history. Created in 1937, the massive mural was a response to the bombing of the Basque town of Guernica by German and Italian planes during the Spanish Civil War. Measuring over 25 feet wide, the painting is rendered in a monochromatic palette of grey, black, and white, which Picasso used to mimic the starkness of newspaper photographs and to emphasize the grim subject matter. The work is filled with Cubist symbolism: a gored horse, a screaming mother holding her dead child, and a bull representing brutality or darkness. Picasso famously refused to allow the painting to return to Spain until democracy was restored; it finally arrived in Madrid in 1981, years after both Picasso and General Franco had died. Today, it hangs in the Museo Reina Sofía and serves as a powerful reminder of the horrors of war and the enduring role of the artist as a social critic.