It's hidden in Celestic Town.
from the foreign guy
celestic town, wild poliwhirl
When playing the Pokeman light platinum destroy huge rocks you have to use route 509.
it for the powerful Pokemon home "spritomb!"
you must HM rock smash.
you need rock climb
You can use any Pokemon that is able to learn Strength to push rocks.
U can sometimes find them on wild poliwhirl
What?!?
Use the hm strength.
cheesy cheese pufs smell cheese
You need the move rock smash