Voronwë guides Tuor to Gondolin
Event Type: General
Age: 1st Age
…But Ulmo, who had chosen him as the instrument of his designs, caused him to go by secret ways out of the land of Dorlomin, so that his going was hidden from all the servants of Morgoth; and he came to Nivrost. But there, becoming enamoured of the Sea, he tarried long; and in the autumn of the year Ulmo himself appeared to Tuor, and bade him to depart, and go to the hidden city of Turgon. And he sent to him Voronwë, last of the mariners of Turgon, to guide him; and Voronwe led Tuor eastward along the eaves of Eryd Wethion to Ivrin. (And there they saw Turin pass, but spoke not with him.) And at the last by the power that Ulmo set upon them they came to the guarded gate of Gondolin. There Tuor was brought before the king, and spoke the counsel of Ulmo, bidding Turgon ... depart and abandon the fair and mighty city that he had built, and go down to the Sea. But Turgon would not listen to this counsel; and [Maeglin later >] Glindur his sister-son spoke against Tuor. But Tuor was held in honour in Gondolin, for his kindred's sake.
The War of the Jewels, Part 1, The Grey Annals
There are other versions of this story, with an alternate date of 496 in The Lost Road version. The most detailed version of the story is in Unfinished Tales, Of Tuor And His Coming To Gondolin