Gondolin is the Elvish city hidden in a valley during the First Age of Tolkien’s legendarium.
The city is founded by Turgon, a Noldorin Elf, in a concealed valley surrounded by mountains. Its location is protected from the forces of Morgoth, the primary enemy of the Elves and Men in the First Age. Gondolin’s secrecy allows it to endure for centuries while much of Beleriand is at war.
Tolkien describes Gondolin as one of the great hidden kingdoms of the Elder Days. Its eventual fall follows the betrayal of Maeglin, who reveals its location to Morgoth after being captured and tempted. The city is then attacked, and its people flee through a secret route.
Gondolin is distinct from Nargothrond, another major Noldorin realm, and from Doriath, the woodland kingdom of Thingol and Melian. Its story is central to The Fall of Gondolin, one of Tolkien’s major First Age tales.