The Encircling Mountains of the Echoriath protected Gondolin from the spies of Morgoth, but they were not entirely impassable. To the north of the city lay a treacherous and difficult pass through the mountains, leading along the side of a cliff face with a deep chasm to the west. This high pass was known in Elvish as Cirith Thoronath, the Eagles' Cleft, and it was through this narrow way that the survivors of Gondolin escaped after the fall of that city in I 510.