Its sky pillar..once u go to sootopolis,u need to go to the cave of origin..once ur there,talk to wallace,then head to sky pillar..he will be there waiting for u ..once u talk to him,he opens the door for u to catch Rayquaza.
the door will be open after you solve the crisis between kyogre and groudon.
You need to beat the Elite Four.
You must beat the elite four and the champion then go there and it will be open
wake up raquaza in the sky pillar
a key is used to open a door in a random floor. . . you face the door and use the key and there is a item in it. __
after you beat the elite four the door at sky pillar should open
You first have to beat the Elite Four and the Champion After that, the door should open.
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fortess
you use your arrows and shoot at a switch around there the door will open .careful not to get blown away
beat the other gyms and it will open. It is giovanni -------------------------------------------------------------------------------------------------------------- DO NOT LISTEN TO THAT ONE You are supposed to get to the underwater cavern and beat team magma then go to sky pillar
it was a military fortess