First you have to go to the Spear Pillar to obtain Dialga. So make sure you save that Master ball you got from Cyrus. To go to the Spear Pillar you need to enter mt.coronet. Make sure you have tons of super repels, escape rope, healed pokemon, full heals, potions, full restores, and also make sure your pokemon are strong. After the biking path from eterna city enter through the entrence on the right. Your gonna have to find your way there. After you exit you will be in Snowpoint city. There you go left over the grass on back into coronet. you battle the galactic guys and go to the right. After you find your way you enter in the spear pillar. Use your potions now. You will doube battle with the most powerful grunts. Then you rival will join you to battle Commander Mars and Commander Jupiter. After you win you friend will heal you pokemon. Then you battle Cyrus. After that you go up to Dialga and catch him with the master ball. Then go to SunnyShore city and the guy who says there is a black out will be gone and you can enter.
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.