Pokémon Diamond and Pearl/Hall of Origin

The Hall of Origin isn't really a "Hall" it's more like a tiny glass platform above the Spear Pillar with on it.

The only way to get there is to cheat the game to give you the Azure Flute in Mystergy Gift. NOTE: It won't work if you just cheat the flute into your bag, you MUST receive it in a mystery gift. This can be done with either an Action Replay code or using Pokesav.

After receiving it, go all the way up Mt. Coronet and into Spear Pillar. Once in, the game will ask you if you want to play the flute. Well of course you do! Play it and a stair case will appear. '''THIS IS WHERE YOU SAVE. Once you get to the top of the stairs you will challenge Arceus automatically.'''