And what about inside the Earth? Christians have said that is where Hell is – the Book of Enoch tells how fallen Angels were cast into its depths, and some forms of Buddhism have stated that “Ghosts live in a world located five hundred leagues beneath the surface of the Earth” (from The Norton Anthology of World Religions, Jack Miles. 2015 W. W. Norton & Co).
Elsewhere on this site I have written about the massive network of subterranean tunnels running around the world, and whole underground cities. Some of them are closer to the surface and were abandoned millennia ago, to be rediscovered by present-day archaeologists. But there are many more remaining in use, deeper down, complete with underground lakes of fresh water and food crops.
In the video below, the host is worried about possible catastrophe to be caused by the Sun – that is something that I am not worried about, but nevertheless, he gives a good outline of some of the subterranean areas we do know about.