Gilfach Ddu (also known as the Dinorwic Slate Quarry Workshops)[1][2] are a series of well-preserved Grade I listed industrial buildings built to serve the Dinorwic slate quarry[3] near Llanberis in Caernarfonshire, North Wales. The workshops compreise a complex of repair and maintenance buildings, that were built in 1870 to build and maintain the machinery used in the quarry.[4] The complex includes saw sheds, patternmaking shops, a foundry with cupola, blacksmiths shops, fitting shops, stores, engine sheds, a canteen, the chief engineer's house, a hand operated crane and two waterwheels which provided the site with its power.[4] Since 1972, the buildings have housed the National Slate Museum.[5]