When the city of Gondolin fell, a remnant of its people were able to escape through a secret passage that Idril had created, leading out into the floor of the valley of Tumladen. From there they were led by Tuor and Idril¹ into the Encircling Mountains, and so made their way into the pass known as Cirith Thoronath. There they were ambushed by watching Orcs commanded by a Balrog. The Exiles survived that trap, but the Elf-lord Glorfindel was slain as he fell from the mountain heights with the Balrog.

After escaping through the mountains, the survivors of Gondolin made their way into the south, and remained for a time in Nan-tathren, the land where the rivers Narog and Sirion flowed together. While there, a longing for the sea fell on Tuor, and also on his young son Eärendil, and so they travelled on to settle finally at the Mouths of Sirion on the shores of the Bay of Balar.