Middle Earth is a fictional world created by J.R.R. Tolkien and featured in his books The Hobbit and The Lord of the Rings. The term 'Middle Earth' is used to refer to the entire world, and the crossword solutions CORE (4 letters) and BILBOSPHERE (11 letters) are two parts of this world. CORE refers to the central region of Middle Earth, while BILBOSPHERE is a term used to describe the area around the Shire, where the character Bilbo Baggins lived.