One of the things which gives The Hobbit and The Lord of the Rings such rich “inner consistency of reality” is the thousands of years of fully realized history which readers at the first printings had no idea existed.  Casual references to a city with a history and artifacts in these scenes are part of the magic of high register – the current story is part of a history.

• 03.035 in Gondolin for the Goblin-wars.
• 03.035 in the ancient tongue of Gondolin;
• 03.035 Foe-hammer that the king of Gondolin once wore.
• 04.033 when the fair elves of Gondolin hunted them
• 05.006 in Gondolin for the goblin-wars
• 05.021 a blade which came out of Gondolin!’

Tolkien, J. R. R., “On Faerie Stories.” The Tolkien Reader. New York: Ballantine Books, 1966 (first Printing). Print.