Gondolin is a fictional city in J.R.R. Tolkien's legendarium, specifically featured in "The Silmarillion." It was a hidden realm built by the Elves, known for its beauty and splendor. Gondolin was founded by Turgon, one of the Noldorin Elves, and was protected by mountains and a secret entrance, making it difficult for enemies to find. The city was ultimately destroyed during the Fall of Gondolin, a significant event in Tolkien's mythology. This tragedy was caused by the betrayal of Maeglin, who revealed its location to the dark lord Morgoth. The fall of Gondolin marked a pivotal moment in the history of Middle-earth.