RE: The B/W Questions and Answers Thread
To give more detail:
After entering the Giant Chasm, go counterclockwise until you approach a boulder. Use Strength from there, and then go clockwise until you can find the exit (you may have to go clockwise instead of counterclockwise the first time to reach the boulder, but I'm not sure on this). Once you reach the exit, you will be in a big area with fog and grass. You want to go in a clockwise spiral until you reach the pond in the center, hugging the inside curve as much as possible. After you do that, go north, and a little bit east, and you should find another cave. You have now found Kyurem's hiding spot.