I got a tip from Johan at work about an interesting book, one that deals with underground wonders. The book is Underland by Robert MacFarlane. I don't really know yet what's inside, but there was a recommendation in New York Times, that can't be bad :-)
See more caving stories at Planetcaver.net, and all Planetskier and Planetcaver stories at Blogspot and TGR! See also my cave map that runs the Psgeo software that has now been open sourced! This article and photos are (c) 2020 by Jari Arkko. All rights reserved.