Have you ever seen Agartha?
I bet you have heard and read a lot of it, but images?
Nope! It's always the same fake fantasy RPG, but then how come the inner sun? How come the hollow earth?
The most important part is not having the biased "sky on top" as usual. like, if agartha is in the center of earth, there can not be a blue sky on the top part of the image. then the inner sun, the sun cannot be on top neither near bottom (as a sunset), it's the clouds which will give the effect. there is an image of a night too, but it's the inner sun fully covered in clouds.
Also added a sort of a guide on HuggingFace