How do you open the door in sky pillar in emerald?

After you defeat Team Aqua and Team Magma's bosses, Wallace will take you to the Sky Pillar to awaken Rayquaza. Going through the incident in Sootopolis City, you can afterward return to the Sky Pillar to catch Rayquaza.

This time, Sky Pillar will be more difficult to travel through, and Rayquaza is Lv. 70.