In the town you are in now, Sootopolis City. There is another cave, The Cave Of Origin. Groundon is in there now, once you go in there you get a chance to catch him, and after that the Gym will open.
PS, Don't use youir Master Ball on him and Pack a Electric and a Grass type in that Gym
« Last edited by BeN_b! on Jul 2nd 2006 »