HERCULES'S Pillars, in antiquity, a name given to two lofty mountains, situated one on the most southern extremity of Spain, and the other on the opposite part of Africa. They were called by the ancients Abyla and Calpe. They are 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 Atlantic seas.