Ok, the photos do not do justice to this stunning chamber! It was only "opened" to the show cave in 2015! (The last time I visited was in 1990!!)
The caves are still explored very regularly by cave divers, and the decision was made to connect chamber 9 to chamber 20 via a tunnel in 2015.
What is visible in the images is the result of melt-water from the end of the last ice age. It has sculpted the rocks into valleys, ridges and crevasses.
It is, as far as we know, the largest example of this in the whole of the UK.