answer the Question and go through the door the answer arrow is pionting to if u get it wrong you have to battle a trainer
Velistone City
sunnyshore city which is located near valor lakefront
find a way to clestick town and get surf then go to hearthome city
Saffron city.
Cinnibar island.
Saffron city.
Beat the Gim Leader.
the fifth gym on Pokemon diamond is the one in herthome city,
same as diamond and pearl. in snowpoint city
On cinnabar island but you need to get the secret key in Pokemon mansion first.
In Pewter City, past the Varidian Forest.
try specifing which version first. :)