If you are playing platinum, you should defeat Cyrus and the commander and set the three mews free. If you go back to that area, the painting should be smashed and Looker should come and give you the mission to stop Cyrus, then send you off with a black Flute (no special purpose, it just lowers the chances of a wild Pokemon encounter).
it should be in the center zone
It mostly depends on where you are.
in mt cornet
Go to Eterna City, go down to Cycling Road. When you reach the end and come out, go to your right to see trees blocking the way, use HM1 Cut there. Go north (up) and you will see a cave, inside you can find Bronzor. Hope I helped.
No . Instead, you use rock climb, go to the mountainside, go up 2 staircases, go down 1 staircase ,and go in the cave.
If you enter Mt Coronet from Route 216 (from Snowpoint City), you should run into the cave almost immediately.
With the TM move strength you can move the boulders in the cave that leads to mt. cornet.
go to mt. cornet and go a cave
To get to the top of Mt. Cornet you have to beat the team Galactic Eterna City and Veilstone buildings(otherwise there will be a cave painting blocking the path in Mt. Cornet) and enter Mt. Cornet from the Oreburg-Hearthrome City entrance(This is the ONLY entrance to the summit of Mt. Cornet. The other entrance takes you on the path to Snowpoint City). You need the HMs Rock Climb, Rock Smash, Strength, and Surf (Defog won't work in the cave). Also, when you get to the crumbled cave painting, Looker will give you a Black Flute, which lowers the chance of you running into wild pokemon.
You have to catch an Abra at a mt. cornet cave opening and train it.
in mt cornet in mt cornet
that is where you get palkia or dialga. Do you have all 8 badges yet?
you have to go thru the cave that leeds to mt cornet(at the bottem)and just keep climbing.you'll need certain Pokemon that have the right HMS to get thru the obsticals like boulders n stuff.
I'm pretty sure there at the top of mt. cornet and where you found dailga and palkia if you haven't found them in the game i just told you =] this guy is wrong about where the orbs are but it is in the cave and the cave is in a cave and you wak by it when you are exploring in mt. cornet so look down where you walk when you see water [ peace :)
deep inside the cave make sure to have plenty of repels it is a long walk. :)
You need to of released the lakePokemon (Azelf, Mesphrit, and Uxie). The you can go there and the cave painting will be demolished.
there is another entrance on the left