Gondolin is the ancient city destroyed in J.R.R. Tolkien’s First Age story The Fall of Gondolin.
Gondolin was a hidden Elven city founded by Turgon in a valley surrounded by mountains. It was established during the First Age of Middle-earth and remained concealed from Morgoth for centuries.
Its location was eventually betrayed by Maeglin, who had been captured by Morgoth. Morgoth’s forces attacked during a festival, and the city fell after a major battle. Tuor, Idril, and their son Eärendil were among the survivors who escaped.
Gondolin is not the same as Gondor, the later human kingdom in the south. Nargothrond and Doriath were also important First Age realms, while Tirion was an Elven city in Aman rather than the hidden city destroyed in this story.