get kyogre and then he can go to all regions so he transports you there
you do ecruteack city
goldenrod city in a house there is a lady
in saffron city
you have to beat team rocket in goldenrod city
Blackthorne City, to the west of the pokemart
you do ecruteack city
Blackthorne city is not in Pokemon Diamond but in Pokemon Heart Gold/Soul Silver
goldenrod city.
it is in the city after pewter
it is in goldrod city
in ecruteak city
By going to saffron city.
goldenrod city in a house there is a lady
its in blackthorn city behind the gym
on the far left in the city
Pewter City, in Kanto.
in viridian city