They were digging for slate at Delabole when Christopher Columbus sailed the ocean blue, and they still are digging today. In fact, the Delabole slate quarry has probably been around for about 1000 years. It is, without contest, the oldest working slate quarry in England, and it was once the largest man-made hole in the world.
Located in the Cornwall region in the Southwest of England, the pit is 425 feet deep and a mile and a half in circumference. Looking into the massive hole, which has a blue, mineral-rich pool in its center, it is astonishing to think that there were once over 1000 people working inside. The quarry supplied slate, used in tiling, roofing, and other construction disciplines, to all of Britain and foreign countries as well.
Though the quarry currently only employs about forty workers, using the latest technology–diamond wire saws, as opposed to the dangerous blasting method of the 19th century–Delabole still manages to harvest 120 tons of slate per day.