Radiant Garden (Ultima)

Radiant Gardens in Kingdom Hearts Ultima would play a major role as both the hub world as well as the mode of transport between worlds and constellations.

The world consist of 2 major parts, the town of Radiant Garden and the castle Hollow Bastion. Radiant Gardens would be you can purchase and synthesise equipment while the castle role is where the Crystal Chamber is.

The Grand Hall is where the Crystal Chamber is, replacing the Dark Depths. (Where Sora and company fight Behemoth, and the Keyhole here is sealed.)

Aerith, with the powers of Holy, is able to pass all of Radiant Garden through the Realm of Light, when she prays for this spell at the Crystal Chamber. It is this way Radiant Garden can move between the constellations that allow Colin to access other worlds via Lanes Between.