I just don't know if enough has been made of the Dark Knight Rises teaser trailer which debuted before Harry Potter a few weeks ago. Maybe it helps that I saw it that very night on a digital screen in a theater with mind-blowing sound. I flipped the eff out. I think that was a warranted reaction, though.
I just came across a fantastic shot-by-shot breakdown of the amazingness that is this teaser, so you should read that, and I'll just add some stuff.
First of all, the author does a fantastic job of drawing the visual parallel between Batman and Gotham City as presented in the trailer. Batman is an Epic hero, like Achilles or Odysseus before him. Or Jesus for that matter. In Nolan's Bat-verse he follows the same pattern they all do point-for-point. The author of the article relates Nolan's Batman to Joseph Campbell's "hero's journey," which is entirely valid. The majority of what Campbell did in comparative mythology is good and true.
At any rate, an Epic hero is always defined by his polis, the city from which he hails, for which he fights, and to which he hopes to return as king (if he's not already). For Odysseus it was Ithaca, for Aeneas it was Rome, for Christ it's the New Jerusalem. Not only is the hero defined by his polis and vice-versa, however, their fates are so completely intertwined that one could almost say the hero is the city, or at least an extension of it. Likewise with Batman and Gotham City.
As we hear Ra's al Ghul repeat from Batman Begins, a hero must be "more than a man." He must "devote himself to an ideal." A hero is not a man; he is a principle. As Alfred points out in The Dark Knight, he cannot be bound by the concerns of ordinary men. This was Hector's mistake in The Iliad, putting family and clan before duty, honor, justice, and his polis.
Much of the teaser consists of Gotham buildings in the process of crumbling. This is because Batman too is crumbling. He is Gotham's savior and champion. If he falls, all Gotham falls. Throughout the trailer Batman himself is portrayed as weak and ready to break.
(Interestingly, Batman and Commissioner Gordon can also be identified with one another. Their journeys parallel each other perfectly, as they do almost page-for-page in Nolan's inspiration Batman: Year One. As Gordon says in the teaser, they "were in this together." With Batman and Gotham hurting, it only makes sense that Gordon would end up in a hospital bed too.)
The Epic hero's journey can be divided into three stages: The Battle, The Journey (in which the hero descends to the Underworld), and the Homecoming, at which point he (re)founds his city and establishes the peace for which he fought. These three stages mirror the Tragic and Comedic stages, Infernal (Hell), Purgatorial (Purgatory), and Paradisal (Heaven). It is in Batman Begins that Batman must fight for his very right to exist. He struggles against all reason to accomplish his goal: to establish himself as an effective source of justice and order in Gotham. By the end of the first film he has successfully done this and won a small victory.
In The Dark Knight, Batman descends into the Underworld of the Joker's chaos, as does all of Gotham with him (even its favorite son Harvey Dent). Batman must wade through the Joker's madness before peace can be reign. Like the journeys of Odysseus and Aeneas, Batman's is a journey of purgatorial suffering, a journey through the valley of the shadow of death. Fittingly, Gotham will be couched in the cold death of winter for portions of The Dark Knight Rises.
Batman and Gotham have not yet emerged from this valley into which the Joker cast them. The Joker made Gotham question the validity of Batman's role as King, to the point that Batman himself questioned it. Something we know he continues to do into The Dark Knight Rises from his conversation with Gordon.
Bane is here to kick Batman, Gotham City, and Commissioner Gordon while they're down. The Joker has left them tired and weak, and Bane wants to take advantage of the situation and usurp Batman's throne, exactly as he seeks to do in the comic books. It would not be insignificant or misguided to compare Bane to the suitors which attempt to usurp Odysseys' throne in his absence. I guarantee that the climax of The Dark Knight Rises will be Batman returning to his great hall to cleanse it of Bane's evil.
By the way, it should be clear that the perfect title for this last installment would have been Gotham City, as this is when Batman must "rise up" and defeat the evil outside and within once and for all, inaugurating an (as far as we know everlasting) era of peace and order in his kingdom. Understandably, though, they wanted to reference their previous blockbuster explicitly and went with the second-best choice.