The Earth's Core.
H O T !
Well…Its either the core or nickel/iron core…OR its "middle earth" the place where hobbits, orcs, elves and humans live battling it out for dominance in the never ending fight between good and evil….
it's called the core, it is round and solid
Well, unless they decided to call it something else in the 30 years since I learned it. It's called the core.
The middle of the earth is the core. What we do know about the core — that there is a solid inner core of pure iron the size of the Moon, an outer liquid core rich in iron the size of Mars, and an irregular boundary between the liquid core and the bottom of the rocky mantle — comes mostly from studying how seismic waves travel through the earth.