first you must go to mt. coronet on the side of orbourg city and defeat Cyrus and afterwards you should be able to get pass.
It is sunny in Sunyshore City.
you have to get dialga after you could go to sunnyshore city.
Very north of sunyshore city.
Sunyshore City
Jasmine on the beach in Sunyshore City.
In Diamond, you can obtain a Water Stone in the underground in Sunyshore City.
Go up to the Lighthouse in Sunyshore City. You should see him there. Talk to him and then return to the Gym.
Sunyshore city, where the last gym badge will be.
spear pillar on diamond, pearl, and platinum.
Climb To The Top Of MT.Coronet,and catch or deafeat Dialga There.
Capture palkia in peral, dialga in diamond, and giritina in platnium
To unlock Sunyshore City in Pokémon Pearl and Diamond you have to beat Team Galactic. They can be found at Mt. Coronet.