This is an absolute outrage.
Also known to some as "spelunking."
Yeah, it's super weird, but very athletic and testing of one's wits.
Here's a recent video of a trip into one of England's most difficult caves:
If you're ever interested in doing something like this, here's the group I belong to. We have meetings the first Wednesday of every month, and monthly trips, usually to Indiana caves. http://www.cigcaves.com/
Great to see a terrific national publication giving Sun King some love.