The Silmarillion

Thus it was that the son of Huor rode across Tumladen, and came to the gate of Gondolin; and passing up the wide stairways of the city he was brought at last to the Tower of the King, and looked upon the images of the Trees of Valinor. Then Tuor stood before Turgon son of Fingolfin, High King of the Noldor, and upon the King's right hand there stood Maeglin his sister-son, but upon his left hand sat Idril Celebrindal his daughter; and all that heard the voice of Tuor marvelled, doubting that this were in truth a Man of mortal race, for his words were the words of the Lord of Waters that came to him in that hour. And he gave warning to Turgon that the Curse of Mandos now hastened to its fulfilment, when all the works of the Noldor should perish; and he bade him depart, and abandon the fair and mighty city that he had built, and go down Sirion to the sea.

Then Turgon pondered long the counsel of Ulmo, and there came into his mind the words that were spoken to him in Vinyamar: 'Love not too well the work of thy hands and the devices of thy heart; and remember that the true hope of the Noldor lieth in the West, and cometh from the Sea.' But Turgon was become proud, and Gondolin as beautiful as a memory of Elven Tirion, and he trusted still in its secret and impregnable strength, though even a Vala should gainsay it; and after the Nirnaeth Arnoediad the people of that city desired never again to mingle in the woes of Elves and Men without, nor to return through dread and danger into the West. Shut behind their pathless and enchanted hills they suffered none to enter, though he fled from Morgoth hate-pursued; and tidings of the lands beyond came to them faint and far, and they heeded them little. The spies of Angband sought for them in vain; and their dwelling was as a rumour, and a secret that none could find. Maeglin spoke ever against Tuor in the councils of the King, and his words seemed the more weighty in that they went with Turgon's heart; and at the last he rejected the bidding of Ulmo and refused his counsel. But in the warning of the Vala he heard again the words that were spoken before the departing Noldor on the coast of Araman long ago; and the fear of treason was wakened in Turgon's heart. Therefore in that time the very entrance to the hidden door in the Encircling Mountains was caused to be blocked up; and thereafter none went ever forth from Gondolin on any errand of peace or war, while that city stood. Tidings were brought by Thorondor Lord of Eagles of the fall of Nargothrond, and after of the slaying of Thingol and of Dior his heir, and of the ruin of Doriath; but Turgon shut his ear to word of the woes without, and vowed to march never at the side of any son of Fëanor; and his people he forbade ever to pass the leaguer of the hills.

And Tuor remained in Gondolin, for its bliss and its beauty and the wisdom of its people held mm enthralled; and he became mighty in stature and in mind, and learned deeply of the lore of the exiled Elves. Then the heart of Idril was turned to him, and his to her; and Maeglin's secret hatred grew ever greater, for he desired above all things to possess her, the only heir of the King of Gondolin. But so high did Tuor stand in the favour of the King that when he had dwelt there for seven years Turgon did not refuse him even the hand of his daughter; for though he would not heed the bidding of Ulmo, he perceived that the fate of the Noldor was wound with the one whom Ulmo had sent; and he did not forget the words that Huor spoke to him before the host of Gondolin departed from the Battle of Unnumbered Tears.

Then there was made a great and joyful feast, for Tuor had won the hearts of all that people, save only of Maeglin and his secret following; and thus there came to pass the second union of Elves and Men.

In the spring of the year after was born in Gondolin Eärendil Halfelven, the son of Tuor and Idril Celebrindal; and that was five hundred years and three since the coming of the Noldor to Middle-earth. Of surpassing beauty was Eärendil, for a light was in his face as the light of heaven, and he had the beauty and the wisdom of the Eldar and the strength and hardihood of the Men of old; and the Sea spoke ever in his ear and heart, even as with Tuor his father.