Jarmo and I managed to get a picture of the Högberget cave in the cover of the Cave Radio and Electronics Group (CREG) journal!
You can read the journal here. You'll need a subscription to read, but it is only 4£ per year. You can also subscribe to the more general Cave and Karst Science journal at the same place.
Read more urban exploration stories from theurbanexplorer.net, and other underground stories from planetcaver.net. Read the full Planetskier series at planetskier.net, or all blog articles from Blogspot or TGR. Photos, videos, and text (c) 2021 by Jari Arkko and Jarmo Ruuth. All rights reserved.