well after you beat the elite four you go to just below snowpoint to the sailor that earlier said "i want to take a champion on this boat" and then he takes you to the battle zone. depending on whether or not you have filled up the pokedex you can go to survival and resort area and mess around there.
when you complete your pokedex you talk to professor rowan and then oak comes in and gives you the national dex. you can then also transfer Pokemon [such as rayquaza, kyogre, groudon, etc.] from ruby, sapphire, emerald, leafgreen, and fire red and then get them at pal park.
also if you talk to Bebe in hearthome city she'll give you an Eevee. [i recomend evolving it into a glaceon.]
Not to mention many many legendary Pokemon you can still catch now that you have the national dex. including giratina, heatran, cresselia and rotom.
have fun.
You then have to beat Cynthia
No you don't.
His lab.
yes there is it is...... 5ty57djsl
Well,Level 70-100 Is A Good Level To Beat The Elite 4.
You then have to beat Cynthia
an level hundred
No you don't.
Then you beat them:)
His lab.
beat the elite four!
after u beat the elite four
You have to migrate them, which I think can only be done when you beat the elite four.
beat the elite four and become champion
yes there is it is...... 5ty57djsl
Well,Level 70-100 Is A Good Level To Beat The Elite 4.
When you beat the elite four in Diamond/Pearl you can migrate Pokemon from your GBA games.