Are you a noob? There is no bronco city RETARDO.
You need to calm Dialga on Mt. Coronet.
To unlock Sunyshore City in Pokémon Pearl and Diamond you have to beat Team Galactic. They can be found at Mt. Coronet.
you must go to the spear pillar in Mt.Coronet.then you fight dialga and unlock sunnyshore.enter mt.coronet from route 207(or 8) near the hearthome city
You have to have defeated Team Rocket in their Veilstone City HQ.
Synshrone city is not a real city in Pokemon Diamond.
you have to unlock celestic town
Blackthorne city is not in Pokemon Diamond but in Pokemon Heart Gold/Soul Silver
heck nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnoooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
Fortree City is a location exclusive to Pokemon Ruby, Sapphire and Emerald. This means it is impossible to visit Fortree City on Pokemon Diamond.
the fifth gym on Pokemon diamond is the one in herthome city,
The first gym in Pokemon diamond is in Oreburgh City
south of hearthome city