Yes actually there is.....
>Once you have captured Regirock, Regice and Registeel, you now will be able to access the Colossal Pokémon, Regigigas. If you bring the three Pokémon with you to where Regigigas sleeps in the basement of Twist Mountain, and interact with it, it will awake.
So catch Regice,Regirock, and Registeel, then bring them to the sleeping Regigigas and he will awaken and battle you. You can precede to catch him.