The Gates of Alexander, also known as the Caspian Gates, are one of several mountain passes in eastern Anatolia, the Caucasus, and Persia, often imagined as an actual fortification, or as a symbolic boundary separating the civilized from the uncivilized world. The original Gates of Alexander were just south of the Caspian Sea, at Rhagae, where Alexander crossed while pursuing Darius III. The name was transferred to passes through the Caucasus, on the other side of the Caspian, by the more fanciful historians of Alexander.