HERCULES'S Pillars, in Antiquity, a name given to two lofty mountains, one situated on the most southern extremity of Spain, and the other on the opposite coast of Africa. They were called by the ancients Abyla and Calpe. They were reckoned the boundaries of the labours of Hercules; and, according to ancient tradition, they were joined together till they were severed by the arm of the hero, and a communication opened between the Mediterranean and the Atlantic.