hurin and huor in their youth entered the elvish city of gondolin , hidden within a circle of high mountains , as is told in the children of hurin ( and # 8224 ; ) ; and afterwards , in the battle of unnumbered tears , they met again with turgon , king of gondolin , and he said to them ( and # 8224 ; ) : 'not long now can gondolin remain hidden , and being discovered it must fall . '