The Physical Realm is like a great half sphere, the flat half facing upwards, floating in a giant pool of pure liquefied magic.
The Magical Realm is a place that mortals cannot access – a massive sea of Magic within the Great Bowl.
If someone were to somehow survive getting past the Great Bowl they would find the Void, where other planes of existence sit, and the Darkness ever watching from the shadows.
The Realms of the Great Ones (called moons by many, see Moon Cycles for more information) rotate around the Physical Realm (within the Astral Plane), and when they run low on sustenance they fall into the Magical Realm and continue their rotation, absorbing magical power to rise into the sky once again.
The sun is all the visible brightness of The Light being poured out for mortals to see and have an example of the brightness to strive for. (it is noted that the sun is not to be worshipped, as it is not The Light itself, but simply some of its energy shining for mortal beings, see the Dominion of The Light for more details).
The stars are believed to be different things in different cultures, but many believe them to be great heroes of The Light who now have their own place to watch mortal affairs from. They are often grouped into constellations, warriors and fighters into the Lance, or Scholars into the Long Scroll, or Magic users into the Orb and Staff (etc.), the brighter the star, the more heroic the hero.
The Southern Star is also known as the Star of Guidance, is believed by many to be the Legendary Hero of The Light (ask about Rumors/Legends, Calendar, and Followers of the Path or the Dominion of The Light).
The World Axis – The most common belief is that the Prime Material Plane is the center and all other planes rotate around it. Other planes can be reached by portals or other means. This can be represented with an Orrery.
The Winding Road – Often the belief of Monks and few others, some believe that the planes are all linked as if along a great road, and one can simply walk to the others if they can find the correct path.
A few highly criticized and often shunned scholars and mages theorize that the core of the planet itself is a roiling ball of molten stone, melted by the sheer power that is trapped within. Some even theorize that Physical Realm could be another shape.