Mask-wearing Gregory Peck and Audrey Hepburn hold a sign that says "Clear Air Now." 4 A tourist in Barcelona, Spain, poses for a souvenir photo next to graffiti showing the Mona Lisa wearing a ...

Items like makeshift gas masks made by anti-government protesters at Gezi Park in Istanbul show the "simple means" but "rich ends" of the objects, he adds.

Graffiti of a child throwing a man on the floor in judo attire is seen on a wall amid damaged buildings in Borodyanka [File: Ed Ram/Getty Images] Banksy rose to fame around the city of Bristol, in ...

Items like makeshift gas masks made by anti-government protesters at Gezi Park in Istanbul show the "simple means" but "rich ends" of the objects, he adds.