Olivine city map.
Beat all the gym leaders and Kanto leaders, then beat Elite 4 and champion.
you do not find dialga in Pokemon pearl
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you find dialga in mount coronet
we find dialga in map 3 in Pokemon deluge...
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you pee on him
you dont
in your house
Trade with Pokemon Pearl or Pokemon Platinum
you can find dialga in map 16 you can also find arceus in map 16 too
I don't think Dialga can be hatched from an egg. You can find Dialga at Spear Pillar though.