The Gates of Alexander, also known as the Caspian Gates, were several mountain passes that came to be associated with Alexander the Great. Only the passage at Rhagae between Media and Parthia, which Alexander crossed while pursuing Darius III, is said to be linked with the historical Alexander. In later literature, the Caspian Gates has also been identified with two other locations: the Pass of Derbent, Russia, or with the Pass of Dariel, a gorge forming a pass between Russia and Georgia with the Caspian Sea to the east. Tradition also connects it to the Great Wall of Gorgan (Red Snake) on its south-eastern shore. These fortifications were historically part of the defence lines built by the Sassanid Persians, while the Great Wall of Gorgan may have been built by the Parthians. In the 7th-century Christian Alexander Legend the gates were supposedly transformed to a wall built by Alexander in the Caucasus to keep the apocalyptic nations of Gog and Magog. A similar narration is mentioned in al-Kahf ("The Cave"), the 18th chapter of the Quran. According to the Quranic narrative, Gog and Magog ( ) were walled off by Dhu al-Qarnayn ("possessor of the Two Horns"), a righteous ruler and conqueror who reached the west and the east. The barrier was constructed with melted iron sheets and covered with copper. Literary background The name Caspian Gates originally applied to the narrow region at the southeast corner of the Caspian Sea, through which Alexander actually marched in the pursuit of Darius III, although he did not stop to fortify it. The name was transferred to the passes through the Caucasus, on the other side of the Caspian, by the more fanciful historians of Alexander. Pliny the Elder (23 AD – 25 August 79 AD) in his [[Natural_History_(Pliny)|Natural History]] criticises this error, and distinguishes the Gates of the Caucasus from the true Caspian Gates through which Alexander passed. He describes the Gates of the Caucasus as a vast natural feature in a mountain chain rent asunder. Here, he says gates with iron covered beams have been placed above a horribly odorous river, along with a fortress to bar the passage of the innumerable tribes. These gates divide the world into two portions. Josephus, a Jewish historian in the 1st century, gives the first extant reference to gates constructed by Alexander, designed to be a barrier against the Scythians. According to this