You find it in the basement of the Galactic Warehouse
Get the national pokedex
The best way to unlock the special items on Pou is to play the games and take good care of your pet. As you progress through the levels, you will unlock special items.
You must have the event regigigas to open the gate
You can't only in Pokemon Platinum unfourtunatly.
You have to get every trophy and unlock everything.
Yes you need to go to a special place to unlock them though.
Enter the password at the password prompt. KNOX: Unlock Last Man Standing Challenge YTHZ: Unlock Special Challenge #1 JRWS: Unlock Special Challenge #10 WIKF: Unlock Special Challenge #11 FAMQ: Unlock Special Challenge #12 GVDL: Unlock Special Challenge #2 RBSG: Unlock Special Challenge #3 BSLU: Unlock Special Challenge #4 MRHC: Unlock Special Challenge #5 MNCH: Unlock Special Challenge #6 KDTR: Unlock Special Challenge #7 DOPX: Unlock Special Challenge #8 PRGN: Unlock Special Challenge #9
Unlock all the other trophies, then you will get the platinum.
Head back to Veilstone City. When you arrive at Veilstone City, make your way to the Galactic HQ and talk to the Grunt standing next to the satellite dish. He'll drop the Storage Key before running off. Pick up the key, and head to the Galactic Warehouse to unlock the rusty door. You'll now be in the inside the Galactic HQ.
get to level 60
To get the platinum trophy you must unlock all the other trophies.
unlock codes
Get the national pokedex
You have to have defeated Team Rocket in their Veilstone City HQ.
NO! You can only unlock pal park on platinum, diamond and pearl
You cannot capture Rotom is HG or SS. The only way to get one and unlock the special room in Silph Co. is to trade from Diamond, Pearl, or Platinum.
There are only 3 possible ways to get Regirock in Platinum. 1. Migrate it from Ruby/Sapphire/Emerald. 2. Unlock its secret area with the special Toys 'R' Us Level 100 Regigigas. 3. Trade for it over Wi-Fi.