In Pokemon platinum where do you find the orbs that Palkia and dialgahold?

go to the mt.cornet entence near celestic city then you got to an etrence where you will see a waterfall use surf and then waterfall it will take you to an opening go inside and there will be 2 pokeballs one holds the adament orb and one holds the lustrous orb you need to catch dialga and palkia firt to get them though