Cornwall 51
Image by thesweetcheat
Cornwall

Cornish books?

This site might be interesting, try the link to the fougou description. Not sure whether you can just walk in, but might just be worth asking

http://www.caer.co.uk/

Sorry, just spotted the location has been sold and is probably no longer accessible. Shame, I'd had vague plans about visiting it someday and meditating inside it.