In the Silmarillion, by J.R.R. Tolkien, Gondolin was the Sindarin name for the city of Singing Stone, although the name Gondolin itself means something closer to hidden rock.
Gondolin was founded by Turgon, eldest son of Fingolfin, as a refuge for the Noldor, to postpone the Doom of the Noldor. Ulmo, the Valar in charge of the waters, led Turgon through a dried out underground stream to the valley of Tumladen, in the midst of the Encircling Mountains. Here, along with his people, Turgon built the great city, which was said to be the greatest city of the Elves in Middle-Earth.
Turgon hoped to keep his people safe from the power of Morgoth as long as possible, and he managed to for several hundred years, long after many of his father, brothers and cousins had died. Eventually, however, the power of Angband and the curse upon the Noldor meant that Gondolin, too, would fall.
Doom came through the schemes of Turgon's nephew Maeglin, who had developed an unclean longing for his cousin, Idril, and betrayed the city out of jealousy. Morgoth's forces, including several Balrogs stormed and burned the city. The people of Gondolin who survived the destruction of the city fled to the mouths of Sirion, where they joined other refugees from Beleriand.