The deposits of slate at Recht in eastern Belgium were worked by open-cast methods from the eighteenth century, but in 1886 the brothers Margraff opened a shaft to layers of slate some 60 m below the surface. They employed 25 men but the mine closed before the outbreak of war in 1914. The last open quarry in the area ceased work in 1920. The mine was re-opened as a museum in 2007. Visitors see an introductory film explaining the geology of the area, and the quality of the ‘blue rocks’ before embarking on a tour of the workings what includes a visit to the ‘Cathedral’ chamber from which slate has been removed to a height of 14 m. It is also possible to see remnants of the rail tracks on which blocks of slate were removed from the mine.