The Forest of Dean is formed of a raised basin of palaeozoic rocks folded in the Variscan Orogeny, similar to the South Wales coalfield to the west. Underlain by great thicknesses of the Old Red Sandstone, the basin is filled with Carboniferous limestones, sandstones and coal measures, all of which have contributed to the industrial history of the region. Its highest point is Ruardean Hill ().