I was reading about John Cleves Symmes Jr.'s Concentric Spheres.
Symmes firmly believed, no, he attested that the Earth consists of five (5) concentric spheres as shown in this drawing. Each crust is about 1,000 miles thick and habitable on both the outer convex and the inner concave surfaces. He even said that the mid-point in each crust is also habitable and is filled with gaseous life force, and that there is light source and air filling up the space between the spheres.
Then, something dawned on me.
In Norse mythology featuring Thor and Odin, there supposedly are nine (9) worlds.
If you count the number of surfaces of the five concentric spheres, you get exactly 9 surfaces with only one (the convex) surface for the inner most sphere.
Interesting, isn't it?
The Norse mythology might be based on some level of truth!
If you think the inner most sphere's surface is not habitable since it is the Inner Sun, you may want to read "The Hollow Earth" by Rudy Rucker.
The book, believe it or not, features Edgar Allan Poe, as a character.
I wonder which world Olaf Jansen in "The Smoky God" visited. I think he merely went to the inner concave surface of the outermost crust, not the concave world closest to the inner sun. He described the presence of day and night just like our outermost surface.
Friendly Garden Gnome