In Greek mythology, Atlas is a Titan condemned to hold up the heavens or sky for eternity after the Titanomachy. Atlas also plays a role in the myths of two of the greatest Greek heroes: Heracles and Perseus. According to the ancient Greek poet Hesiod, Atlas stood at the ends of the earth in the extreme west. Later, he became commonly identified with the Atlas Mountains in northwest Africa. Atlas was said to have been skilled in philosophy, mathematics, and astronomy. In antiquity, he was credited with inventing the first celestial sphere. In some texts, he is even credited with the invention of astronomy itself.