 Several large quarries are still at work in the area, providing Carboniferous Limestone for road surfacing and also Pennant sandstone (see picture) - a popular building stone used notably by Thomas Telford for the Over road bridge, spanning the River Severn near Gloucester.The scenic Wye Valley defines the western edge of Dean as well as the England/Wales border.Impressive cliffs have been cut by the river in lower dolomitic sections of the Carboniferous Limestone, most notably at the popular ‘Symonds Yat’ viewpoint, which affords one of the most famous views in England.