[Galadriel55]

Question for everyone: how on earth did Morgoth not realize that Gondolin must be in the one patch of land he can't get to?

We're told that before the Bragollach and Nirnaeth his spies couldn't pass beyond the borders of some elven territories, so it's possible that Gondolin lay somewhere beyond - but that wouldn't make much sense since Turgon was known to have a separate kingdom, and one that none of the other Elves knew about. On the other hand, there's this patch of mountains, that spies can't get through either because of the Eagles and other things. After the Nirnaeth it should have been obvious; the only question would be a suitable entrance. Morgoth really shouldn't have needed Hurin to unwittingly give away the general location. He should have known that already.