Penwyllt

A former quarrying village, quicklime and silica brick production centre, Penwyllt's fortunes rose and fell as a result of the Industrial Revolution in South Wales. At one time its population numbered 500 but by the 1960s had fallen to 20. It is now an important caving centre. Beneath Penwyllt and the surrounding area is the extensive limestone cave system of Ogof Ffynnon Ddu, part of which was the first designated underground national nature reserve in the UK. A corresponding area on the surface is also part of the national nature reserve, on the slopes of Carreg Cadno. (Information taken from Wikipedia)