Gondolin is the hidden Elvish city where Tolkien’s character Tuor arrives in The Silmarillion. The city was founded by Turgon in a concealed valley surrounded by mountains during the First Age of Middle-earth.
Tuor, a human raised by Elves, is guided to Gondolin by the Vala Ulmo’s purposes and eventually marries Idril, Turgon’s daughter. Their son is Eärendil, whose voyage and Silmaril become crucial to the later mythology. Gondolin’s hidden location protects it for centuries from Morgoth, the first Dark Lord.
The city is eventually betrayed and destroyed by Morgoth’s forces. Its fall is one of the great tragedies of the First Age. Gondolin should not be confused with Doriath, another Elvish realm, or Nargothrond, an underground kingdom associated with Túrin. Tolkien also wrote a standalone version, The Fall of Gondolin, published posthumously in 2018.