According to Jacques Herzog in this Met Opera video:
Atilla describes the moment in history where an old world, an antique world is collapsing and something new is rising out of the rubble of the old . . . Verdi's vision . . . basically, [is] based on two images. On one hand is the rubble, is the destruction, is the destroyed world, that we took very literally, even more literally than Verdi probably did, and [the other] is nature, represented by wild nature, very strong powerful nature . . . a forest that was both real, scary, symbolic, magical mystical . . . this romantic moment that you find some times in art, in paintings, where the wood is used as a wild energy that at the same time is something which promises hope.More Opera Chic photo's of the sets and the production - oh, and some singers, too - here.
*note to litigators: reference for satirical purposes only.