With the beginning of the fourth century BC probably comes the first portrayal of the Giants in Greek art as anything other than fully human in form, with legs that become coiled serpents having snake heads at the ends in place of feet. Such depictions were perhaps borrowed from Typhon, the monstrous son of Gaia and Tartarus, described by Hesiod as having a hundred snake heads growing from his shoulders. This snake-legged motif becomes the standard for the rest of antiquity, culminating in the monumental Gigantomachy frieze of the second century BC Pergamon Altar. Measuring nearly 400 feet long and over seven feet high, here the Gigantomachy receives its most extensive treatment, with over one hundred figures.