Go in the sealed chamber on the route west of pacifidlog town to find it you need the HM Dive. Solve the braille puzzle then the rock will open.
you dont open you crush crush CRUSH!
sorry but you can't find it in Pokemon diamond/pearl without migrating regirock from Pokemon ruby, sapphire, or emerald. But I think there is a cheat on the action replay for it, but I don't know the cheat.
rock is in the desert ice is on an island between mr brineys and dewford steel is between lilycove and forttree you have to open the caves 1st though
The braille inside the cave says this: Run around the room. Stay close to the walls. Good Luck.
you open them by teaching a pokemon secret power and then tap A next to the indent.
go to the desert, go way down to the bottom of the desert, go in the cave, go straight up to the writing press "a" then go right twice and go down twice, then use strenght and the door will open.
Forever
well they are secret bases but you need to teach one of ur Pokemon secret power(tm43), and u can get it in slateport city at the open market!(In Pokemon Sapphire).
Pal Park (open after you beat the main game)
beat the second gym leader. hope this helped! : )
The elite four will open and they will be stronger and you can now trade with ruby, sapphire and emerald.
read sign, wait two minutes the door will open
You need to know the move dive and get something from underwater