Altar of Zeus. West front. The Gigantomachy frieze depicts the struggle of the gods against the children of the primordial goddess Gaia, who were snake-footed giants. After the new gods under the leadership of Zeus and with the help of Gaia had overcome the old gods led by Cronus, Zeus then opposed several of Gaia's children, contrary to his promise. Gaia accordingly incited several of her children and could only be victorious with the help of mortals.