Santiago Sierra (born 1966) is a Spanish artist. He lives in Mexico City. Sierra‘s work reflects his views on capitalism, labor, and exploitation. For instance, he paid a group of workers to move a heavy rock from a point A to a point B and vice versa. On another occasion he paid drug-addicted prostitutes from Brazil in their drug of choice to let them have a line tattooed across their backs. He also caused controversy by covering ten Iraqi immigrants in insulating polyurethane foam and waiting for it to harden. Another of his well known projects is a room of mud in Hanover, Germany, commemorating the job-creation measure origin of the Maschsee. In 2006, he provoked controversy with his installation "245 cubic metres", a gas chamber created inside a former synagogue in Pulheim, Germany.