Mike Laycock went down a cavern in Derbyshire's Peak District to see the fabulous Blue John Stone.

It has been described as the prettiest cavern in the North, and it would be hard to argue with that description after paying a visit to Treak Cliff Cavern in the Peak District. This has all the usual features one might expect in a cave - hundreds of stalagmites, stalactites and even helictites (strangely twisted stalactites). But Treak Cliff has one massive added bonus - a series of veins of the rare semi-precious stone known as Blue John. A variety of the mineral Fluorspar, the rock comes in a range of colours including blue, mauve, white and yellow.

The name apparently comes from the French for blue and yellow, Bleu et Jaune, once used by French importers of the stone and subsequently mispronounced by Derbyshire folk.

The weathermen had predicted a nice day, so it was no surprise when I arrived with my family in atrocious wind and rain! The cavern is situated inside Treak Cliff hillside near Castleton, a picturesque little village only 15 miles from Sheffield but a world away from the grimy city. After a quick look round the village, we headed out to the cavern and parked easily on the roadside. There was no charge on a weekday, but you apparently pay for the privilege at weekends and Bank Holidays.

Through the battering winds, we walked up a 100-metre and rather slippery footpath to the cavern entrance part-way up the hillside.

Tours of the caverns are organised every half hour and last for about 40 minutes. We visited the shop while we were waiting and bought a small piece of Blue John for my daughter.

If you're tall, you need to keep your head down for the first few metres on entering the cave. But it's not claustrophobic, and you have plenty of headroom through the rest of the cavern.

After walking only 30 metres, you reach the first of the Old Series of chambers, created by long-deserted streams and where a vein of Blue John can be seen in the roof. But the full beauty is best displayed by the placing of two bowls of the stone inside electric light cases, so that light shines through showing up the pattern of blue, mauve and white bands.

There are also fossils in the rockface from the marine life in the area when the limestone was formed some 330 million years ago.

The caves go by a series of dramatic names. A six-metre high opening is known as the Witches Cave because the shadow cast by the lighting on the cave wall looks rather like a witch riding her broomstick.

The effects get better as you reach the New Series of Caverns, discovered in the 1930s, and enter the enormous Aladdin's Cave, with multi-coloured rock buttresses, numerous slender stalactites and a group of large stalagmites known as the Seven Dwarves and thought to be up to 70,000 years old.

Then there's Fairyland, with translucent and transparent formations, the Dream Cave with stalactites dripping with water and finally the Dome of St Pauls, some 11 metres high, and with a range of rock colours from orange, red and brown to blue, green and purple. This is well worth a visit, and you can do so throughout the winter with one added bonus - you are guaranteed a brief escape from the weather outside.

Fact file

Treak Cliff Cavern, Castleton, Derbyshire.

Open daily from 10am to 5pm over next few days, but from 9.30am to 4pm from November 1.

Admission: £5 for adults, £3 for children aged 5-16, under fives free. Family ticket (two adults, two children) £14.

No disabled access.

To get there: Take A64, A1 and M1 to Barnsley. Leave at junction 36, then take A61, A6101, A57, A6013 and A625 to Castleton.

Further information, telephone: 01433 620571.

u This is the last Day Out feature of this year. For more ideas on how to spend your leisure time check out our website: wwwthisisyork.co.uk.