Gondolin is the secret kingdom ruled by Turgon in J.R.R. Tolkien’s First Age stories.
Gondolin was an Elven city hidden in a valley surrounded by the Encircling Mountains. Turgon, a king of the Noldor, founded and ruled it during the wars against Morgoth. Its concealment allowed the city to endure for centuries while remaining a major target of Morgoth’s enemies.
The city was eventually betrayed by Maeglin, who revealed its location to Morgoth. Gondolin fell in a devastating assault, and survivors including Tuor, Idril, and Eärendil escaped through a secret passage.
Gondolin is distinct from Doriath, the woodland kingdom of Thingol, and Nargothrond, the underground realm associated with Finrod and later Túrin. These kingdoms belong to the same First Age history but are not alternate names for Gondolin.