Gondor is a human city known as The White City. This comes from the white tree in the center of it. It always inspires the citizens. Here, a huge battle in which Sauron sends all of his troops to fight takes place. The orcs are destroying the city here and just when it looks like the kingdom of man will fall, Aragorn comes with an army of ghosts. He found them in a cave that no man ever returns from. They were in the debt of the king of man, Aragorn. With his sword, Anduril, they followed him to the battle, where they wiped out the enemies.
I did not know all of this, so please check out my references.