The punishment of Prometheus as a consequence of the theft of fire and giving it to humans is a popular subject of both ancient and modern culture. Zeus, king of the Olympian gods, sentenced Prometheus to eternal torment for his transgression. Prometheus was bound to a rock, and an eagle—the emblem of Zeus—was sent to eat his liver (in ancient Greece, the liver was often thought to be the seat of human emotions). His liver would then grow back overnight, only to be eaten again the next day in an ongoing cycle. Prometheus was eventually freed by the hero Heracles. In yet more symbolism, the struggle of Prometheus is located by some at Mount Elbrus or at Mount Kazbek, two volcanic promontories in the Caucasus Mountains beyond which for the ancient Greeks lay the realm of the "barbarii".