In the northwest of Wales you'll find a long belt of Cambrian slate which was formed about 500m years ago. The line stretches from the Nant Ffrancon valley in the east to Nantlle Valley in the west.
Some of the largest and most productive slate quarries in the world were situated along this belt. The region was known to have "roofed the 19th century world", which in its turn had a significant effect on the lives of the region's people and communities as well as the landscape with its traces still found today.
In the east the slate was garnered through open quarries using the gallery method while in the west slate beds were found beneath the floor of the valley. It was the depth of the slate beneath the valley floor which influenced the quarrying techniques of Nantlle. And the only way to obtain the rock was by digging down and creating large pits.
