Here is a guide to each level of the Hub.
To reach each level, there are stairs winding around the edge of the circular room.
Working from the lowest level to the highest:
Base: Storage
Root Com: The level on which communications from the Root Worlds are received.
Lvl 1: The R Branch level, dealing with all things from the human branch.
Lvl 2: The O Branch Level, dealing with all things from the dragon branch.
Lvl 3: The Y Branch Level, dealing with all things from the uniote branch.
Lvl 4: The G Branch Level, dealing with all things from the military branch.
Lvl 5: The B Branch Level, dealing with all things from the shadow branch.
Lvl 6: The I Branch Level, dealing with all things from the mind branch.
Lvl 7: The V Branch Level, dealing with all things from the fire branch.
Lvl 0: Counter intuitive naming, but this is the level where the workers can hang out and rest.
Rooms: Actually a few levels. Where workers have their own rooms.
Branch Com: Where reports arrive to be sorted into which level they need to go to.
Office: Yoru's office.