You must have caught of faced Dailga/Palkia.

To get to sunnyshore city you must face diagla in diamond or palkia in pearl, to do this
you must p*** all the way through Mr Coronet(might wanna stock up on max repels) and you
also might wanna find a walkthrough as for its pretty confusing, once you have walked
through mr coronet you come to this like big sandy place called the spear pillar, here you
fight all three galactic bosses(so be prepared) then the main boss orders palkia/diagla to
create a new universe that is corrupted by uxie, mespirit and another 1(cant remember
name) wich u catch after, you fight palkia/diagla and catch it, you are then approached my
prof. Rowan, that exits you from the spear pillar, you will now find that the path the fat
guy was previously blocking in lake valor leads to sunnyshore city!