Where is the team galactic warehouse key in pokemon diamond?

Answer 1

the fith gym is in hearthome but first you gotta compete in a pokemon contest its right next to pal park

Answer 2

ok,beat candice(7th gym) then go 2 verity lake(near Twinleaf town) then,help dawn,when u beat the grunts go 2 the HQ in Vielstone,talk 2 the grunt,pick up the item,and VUALA!

Answer 3

Beat the Seventh Gym?? Im only Tring to find the Fifth Gym!!!! O.O GAHH!