My son and I visited Treak Cliff - there was just us and the guide, as they are happy to show you the cavern if there is a minimum of two visitors. We spent the 40 minutes with our jaws agape looking at the Blue John, which is beautiful, and the cave formations of stalagtites and stalagmites. We were shown the tucked away parts of the cavern where mining still occurs, usually through winter months - although the cavern is open right through the year, and the temperature remains a balmy 11 degrees C throughout the year.
There is a shop selling pocket money prices of Blue John and also lovely Blue John pendants, earrings, rings etc., up to £100's (something for everyone's pocket). The stone is so rare - it is the only cave in the world where Blue John is found. The story of how it got its name is interesting too - but you will have to take the tour to find out! There is also a cafe - indoor and out, with lovely views of the valley and surrounding hills. Ever important toilets, and parking is free just outside. Need to be good on your legs as there are steps and a low cave roof in one part of the tour. Our tour was very informative, and the guide was very knowledgable and a pleasure to meet. We would recommend this visit to everyone.