Dinorwic slate quarry, North Wales, UK

Managed another round in my favourite playground - the Dinorwic slate quarry. "It operated from 1787 until its closure on July 4, 1969, and was once the second-largest slate quarry in the world, after Penrhyn Quarry near Bethesda (still operational about 3 miles away. At its peak, it employed over 3,000 workers and produced up to 100,000 tonnes of slate annually. The quarry covered approximately 700 acres (283 hectares) and consisted of two main sections with 40 stepped galleries connected by an extensive internal tramway system using inclines to transport slate."