Outer Planes

The seventeen highest planes of Great Wheel:

The Abyss
Acheron
Arcadia
The Outlands
Elysium
Gehenna
Gladsheim/Ysgard
Hades/The Gray Waste
Happy Hunting Grounds/Beastlands
Limbo
The Nine Hells/Baator
Nirvana/Mechanus
Olympus/Arborea/Arvandor
Pandemonium
Seven Heavens/Mount Celestia
Tarterus/Carceri
Twin Paradises/Bytopia

All of the Outer Planes exist "within" the Astral Plane.