first you have to beat the elite four then go to the pal park near where proffessor Rowans labortory is then catch regirock,regice and registeel then go to snowpoint city tell the lady who guards it and this girl says that you can go in then you could find regigigas the king of the regis.
From romal
Regirock, Regiice and Registeel. if you capture all three and transfer then to Pokemon Diamond/Pearl/Platinum you can go to the shrine in Snowpoint City to battle the master Regigiggas :)
You have to travel through mt.coronet to get too snowpoint city.
snowpoint temple
You need 2 defeat da Snowpoint Gym leader.
you get him at snowpoint temple in snowpoint city but first you need regiice regirock registeel.
Through Mt. Coronet
beat snowpoint gym
by snowpoint city.
in the snowpoint temple
snowpoint temple
In her gym in Snowpoint City.
In Pokemon pearl/platinum/diamond Candice is the 7th/snowpoint city gym leader.