Hollow Earthism

Hollow Earthism is the system of belief that states that the Earth is hollow inside. It originated in folklore, mythologies, and legends, and people in the 16th/17th centuries attempted to justify it (e.g. Edmond Halley). According to other theorists, the lost city of Atlantis, Hyperborea, or anything comparable is on the inner side of the earth. Most hollow-earthers propose the earth is a sphere, but they do not do it in a conventional manner (the conventional idea is that earth is filled with material). Gravity would be generated within the shell, with humans living on the outer surface of the shell.